There have been several repetitive questions about how to use a Color Management System (CMS) to achieve accurate color for those lucky enough to own a display that has one. The purpose of article is to layout in as non-technical way as possible how to do this. Along the way, I'll explain how to set Color/Tint without using filters and how to set Brightness and Contrast without making subjective judgments against test patterns.

Equipment needed

Colorimeter. This is a USB device that you point at the display so it can read the color and light output of the display and then connect to a laptop computer. The most accurate device under $1000 is the X-Rite i1Pro, though it can be a pain to use. A close second is the X-Rite Chroma 5, which is sold only through OEM channels that also sell calibration software. A much less expensive option that is only a little less accurate is the X-Rite Display 2, also sold as the Pantone Eye-One Display LT for less than $150. I would avoid any less expensive colorimeters, as they will not offer what I consider to be a reasonable degree of accuracy.
Calibration Software. You need this to interpret the data that the meter receives. Aside from the very expensive professional tools, there are 3 good choices for amateurs and Prosumers: HCFR (http://www.homecinema-fr.com/colorimetre/index_en.php), CalMan (http://www.spectracal.com/), and ChromaPure (http://www.chromapure.com). HCFR is freeware. CalMan is commercial software that costs about $200, depending on selected options. ChromaPure is also commercial software of my own design which also costs $200 and up depending on options.
Test Patterns. Finally, you'll need some way to get a test pattern on the screen. The easiest way to do this is with a DVD. The GetGray disk, which can be downloaded (http://www.calibrate.tv/) and burned to DVD for about $25. AVS members have created a very nice set of HD patterns (http://www.avsforum.com/avs-vb/showthread.php?t=948496) for Blu-ray and HD-DVD players. Finally, I have created a very simply calibration disc that provides all the patterns necessary for the steps in this guide. See below for a download link.
Light Meter (optional). I have found that a AEMC CA813 illuminance meter is very useful for front projectors and for all measurements that do not require color readings, such as contrast, black level, gamma, and color decoding. It is an accurate, inexpensive standalone tool that is also very easy to use.

Once you have the items in this list, you are ready to calibrate your color.

First, some basic principles and terminology. Color performance is measured in two ways:

Gray scale tracking. This is the aspect of color performance that gets the most attention. It concerns the display's ability to provide a neutral shade of white, all the way from darkest black to the brightest white. If the display can't do this, then it will all of the colors will look very unnatural.
Color Gamut. This is the range of colors that the display is capable of rendering. The gamut is popularly represented by a triangular pattern called a CIE chart or chromaticity diagram. This chart plots colors as xy coordinates. Color also includes luminance, which does not appear on the chart so it must be represented separately. The xy coordinates on the charts plot the primary colors (red, green, and blue) and the white point. The secondary colors (cyan, magenta, and yellow) are derived from the primaries and the white point. All of these points have specific definitions for both standard and high definition. All commercially available video material is mastered according to these standards. If the display cannot reproduce the gamut accurately, then the image will suffer. In recent years it seems that digital displays have gotten increasingly inaccurate in this respect. The only way to fix it is with a Color Management System (CMS). A CMS can make a profound difference to the performance of the display, but few offer one and of those that do not all work properly.

It is important to understand that these aspects of color performance--though in some ways interactive--are for the most part independent. You can have good gray scale tracking and an inaccurate color gamut. The bottom line is that each needs to be adjusted separately.

Terminology

xyY - A common method for precisely measuring color performance. x and y are the coordinates that plot out a color on the triangular CIE chromaticity chart mentioned above. This graphically represents the established definitions of the color spectrum. Y is the brightness of the color. This is not plotted by the xy coordinates.
Saturation - the colorfulness of the color relative to its own brightness. A color's saturation is displayed on the CIE chart as the distance from the white point. Add saturation to a color and it will begin to appear excessively deep and rich-red becomes crimson. Undersaturate a color and it will begin to appear as a less colorful version of a similar brightness--red becomes pink.
Hue - the primary characteristic of color that allows us to distinguish one color from another. A color's hue is measured by its angle to the white point. When a color's hue is off, its appearance will seem contaminated by other colors. For example, red that is too yellowish will begin to seem orange. Blue that is too reddish will begin to appear purplish.
Brightness - the luminance of color. The brightness of color (or white) can be measured by a simple light meter.
Color Decoding - This term refers to a process that is used to lower bandwidth requirements by encoding the native RGB signal into YPbBr (analog) or YCbCr (digital) and then decoding back to RGB prior to display. There are different encoding/decoding standards, so sometimes a poor design may lead to color decoding errors. These errors are primarily seen as primary colors with incorrect brightness and/or secondary colors with incorrect hues. All commercial displays include a Color and Tint control. These are basically color decoding controls, though their effectiveness is extremely limited because Color adjusts the brightness of ALL of the colors and Tint effects hue of ALL of the secondaries. The problem is that displays all-too-often have color decoding errors that effect the colors differently. For example, you could adjust Color/Tint to get the correct brightness of blue and the correct hue of cyan, but the brightness of green and red may still be inaccurate. You could adjust the color control to get red right, but then blue and green would be inaccurate. See the problem? A full set of color decoding controls addresses this problem by offering color/tint controls that operate on red/magenta and green/yellow independently. Then you can use the main Color/Tint controls to adjust blue/cyan.

For all practical purposes the color performance of a display device can be adequately described by the three characteristics defined above--saturation, hue, and brightness. These are abstract concepts and sometimes a picture really does say a thousand words, so here are examples that illustrate the three characteristics of color.

Saturation
http://home.comcast.net/%7Etlhuffman/de/green.jpghttp://home.comcast.net/%7Etlhuffman/de/green_desaturated.jpg

Hue
http://home.comcast.net/%7Etlhuffman/de/green.jpghttp://home.comcast.net/%7Etlhuffman/de/green_yellowish.jpg

Brightness
http://home.comcast.net/%7Etlhuffman/de/green.jpghttp://home.comcast.net/%7Etlhuffman/de/green_dark.jpg

In each of these examples, the green on the right is adjusted by approximately the same amount in the direction of first lower saturation, second yellowish hue, and third lower brightness.

How are these concepts related?

The xy coordinate of a color establishes its saturation and hue. The Y value establishes its brightness. The correct xy coordinate for all primary and secondary colors is defined by reference points on the triangular CIE chromaticity chart. If the color deviates from the reference point by appearing shifted towards other colors on the chart, then its hue is wrong and needs correcting. If a color is shifted closer to or father from the white point on the chart relative to the reference, then its saturation is wrong and needs correcting. Finally, if the color is too bright or too dim relative to the establish standard (not shown on the chart, but determined mathematically), then its brightness is wrong and needs correcting.

Color Definitions

SMPTE-C Rec. 709
x y Y x y Y
R 0.6300 0.3400 0.2124 R 0.6400 0.3300 0.2126
G 0.3100 0.5950 0.7011 G 0.3000 0.6000 0.7152
B 0.1550 0.0700 0.0866 B 0.1500 0.0600 0.0722
Y 0.4209 0.5067 0.9134 Y 0.4193 0.5053 0.9278
C 0.2306 0.3262 0.7876 C 0.2246 0.3287 0.7874
M 0.3144 0.1606 0.2989 M 0.3209 0.1542 0.2848
W 0.3127 0.3290 1.0000 W 0.3127 0.3290 1.0000

EBU DCI
x y Y x y Y
R 0.6400 0.3300 0.2220 R 0.6800 0.3200 0.2095
G 0.2900 0.6000 0.7067 G 0.2650 0.6900 0.7216
B 0.1500 0.0600 0.0713 B 0.1500 0.0600 0.0689
Y 0.4172 0.5018 0.9287 Y 0.4248 0.5476 0.9311
C 0.2197 0.3287 0.7780 C 0.2048 0.3602 0.7905
M 0.3271 0.1576 0.2933 M 0.3424 0.1544 0.2784
W 0.3127 0.3290 1.0000 W 0.3140 0.3510 1.0000
Of these definitions, only the xy coordinates for the primary colors and white point are absolute. The secondary colors and luminance values are DERIVED from the primaries and the white point. If your primary colors measure according to these standards, then this list correctly states the proper specifications for brightness and secondary hue/saturation. However, with a different set of primaries, you would want to shoot for a slightly different set of brightness and secondary hue/saturation targets. The math required to figure out these relationships is too complicated to go into here, but good calibration software should take all of this into account.

Although there are no hard and fast rules about this, I would make color adjustments in the following order:

- Black and White levels
- Gray scale
- Color/Tint
- Color gamut

When finished, go back and remeasure these parameters, because changes in one parameter may have affected the readings for another.

What's wrong with the ISF description of color?

I am a graduate of the ISF seminar, and I think that the organization has performed a valuable service at educating the public about the importance of accurate video. However, the ISF description of color is not entirely clear.

An often-repeated claim by ISF literature is that the characteristics important to image quality can be ranked in the following way:

Contrast
Color Saturation
Color Accuracy
Resolution

Ranking resolution and and contrast in this way seems about right to me, but what in the world is meant by "Color Saturation" that is different from "Color Accuracy"? As I lay out above, all of the standard gamuts have specifically-defined standards for saturation, hue, and brightness. So saturation is just one aspect of color accuracy. Perhaps, this refers a to the fact that a lot of people prefer oversaturated primary colors. If so, then this is an endorsement of color inaccuracy! Surely, ISF doesn't mean this. Perhaps it refers to a purely subjective quality of color that has not been quantified by the established standards. However, color is a fairly well-understood phenomenon. There is, so far as I know, no important aspect of color beyond the characteristics of saturation, hue, and brightness that remain unexplained.

Thus, it seems that "Color Saturation" is either a ghost or simply a poorly-expressed reference to something already known. Some of the statements I have heard ISF personnel make suggests the latter. I think that this may just refer to the brightness of color. If so, then the reference is redundant. Brightness is just one aspect of color accuracy, along with gray scale performance, hue, and saturation.

Thus, the ISF rank of characteristics that are important to image quality really just boils down to:

Contrast
Color accuracy
Resolution

Furthermore, even this revised list is not, I think, quite right. It leaves out two very important aspect of image quality: sharpness and clarity. These concepts are not the same as resolution. Two 1920x1080 displays (equal resolution) can and often do exhibit different degrees of sharpness and clarity. So, what do these concepts mean?


Sharpness is the quality of an image that gives it clearly defined boundaries. This should not be confused with the type of artificial sharpening that you often see in poor DVD transfers an excessive use of the sharpness control on the display. These only result in ringing and edge enhancement, which makes the image worse instead of better. A good example of sharpness can be had by comparing a good plasma or LCD display with a good CRT. CRTs can look very nice, but they simply cannot complete with the sharpness of a plasma or LCD.
Clarity is the quality of an image that appears when the image is free of artifacts. These artifacts come in a wide variety of types and for a wide variety of reasons. They include: poor focus, poor geometry, poor convergence, chromatic aberration, ringing, moire, line twitter, and interference/ghosting/snow (for over-the-air broadcast).

Problems with image clarity are result of the quality of the optics, processing, or mechanical alignment, and involve the display adding something to the image that is not originally there. Problems with sharpness can be influenced by the resolution, optics, and other inherent properties of the display device, and involve the display removing from the image something that was originally there.

The importance of these two factors is perhaps best illustrated by thinking back to the first time you saw a good plasma display fed by a good source. Compared to CRT images, plasmas could produce an image with startling clarity and sharpness that results in an almost scary looking-though-a-window quality that CRTs simply cannot match. The important fact to note for this discussion is that these relatively early plasma displays offered lower resolution, much lower contrast, and often worse color accuracy than the CRTs of the day and they still could look better, sometimes much better.

Another important factor to consider, especially when comparing the importance of sharpness/clarity to contrast, is that these qualities are persistent. This means that they are decisive factors in image quality all of the time. The same cannot be said for contrast. Many types of common images--such as brightly illuminated live sports--are relatively unaffected by the contrast of the display. Contrast becomes increasingly important as the image gets darker, and is thus not a persistent characteristic of image quality, though still a very important one. The same can also be said of color accuracy. Color representation is a persistent quality of the image. If faces are red and the trees glow with a neon green, good contrast won't help.

For this reason, I would rank the elements that contribute to overall image quality in the following way:


Sharpness/clarity
Color accuracy
Contrast
Resolution


Why can't I fix oversaturated colors by simply turning down the main Color control?

This issue comes up often in the context of popular displays that exhibit a strongly oversaturated gamut. The JVC RS1/2/10/15 front projectors are perhaps the best example.

Lacking a full-featured CMS, one is tempted to try to alleviate the problem by simply turning down the main Color control. Turning it down slightly may help somewhat, but anything more than a very small adjustment is likely to make the color worse rather than better. Why? The reason has to do with the fact that, contrary to popular belief, color controls are not engineered to adjust saturation. They are Chroma gain controls. Turn the color up, you increase the chroma of the signal. Turn the Color down, and you decrease the chroma. Although related, chroma and saturation are not the same.

Perhaps the best way to think of the difference is this: Imagine a red patch of color illuminated under a strong, bright light and then imagine the same patch seen under a dim light. As you change the lighting conditions, the red appears more or less colorful. This is chroma. However, the saturation of the color does not change even as its brightness changes dramatically. It will not plot differently on the CIE chart, despite the fact that it is less colorful and significantly dimmer.

Interestingly, the reverse is not true. If you lower the saturation of red, the chroma decreases to approximately the same degree. A less saturated red seems proportionally less colorful, but a less colorful red is not necessarily proportionally less saturated. Consider the two examples below.

Example 1: Chroma change
http://home.comcast.net/%7Etlhuffman/chroma.jpg

Example 2: Saturation change
http://home.comcast.net/%7Etlhuffman/saturation.jpg

The first example mimics the effect of turning down the main Color control. If you turned the Color control all the way down to zero, the the patch would finally lose all of its colorfulness (and saturation) and retain only some residual brightness, appearing as a shade of gray.

The second example mimics what occurs when we decrease saturation using a CMS. The brightness stays relatively constant (it may actually slightly increase), but it loses colorfulness as well.

This should make clear why turning down the main color control is not a good strategy for addressing oversaturated colors. What this does is similar to what you see in Example 1. It will reduce the saturation of the colors, but it will also significantly reduce their brightness. What we need is what is simulated in Example 2.

However, the main color control IS a good tool for adjusting color decoding problems. Unfortunately, it works equally for all of the colors, when what is generally needed is color-specific adjustment.

Note: "Chroma" is a term that has somewhat different meanings depending on the context. Those familiar with video engineering will understand chroma to refer to a rather general concept of color. Video signals contain chrominance and luminance. However, in color science "chroma" has a more specific meaning, which is "colorfulness of a area relative to a similarly illuminated area of white." Color scientists use the term "colorfulness" to refer to what video engineers refer to as chroma.

Luminance vs. Illuminance

You obtain these figures somewhat differently depending upon whether you have a direct view/flat panel/rear projection display or a front projector. For direct view/flat panel/rear projection displays, just attach the probe to the screen and measure directly. The software will measure either in imperial fL (foot-lamberts) or in metric cd/m2 (candelas per meter squared or nits). If you measure in nits, just multiply the output by 0.292 to get fL. If you measure in fL, then multiply by 3.426 to get nits. Nits and fL are both a measure of luminance, which is an emission or reflection of light from a flat, diffuse surface. All colorimeters and spectroradiometers natively measure luminance.

If you have a front projector, it is a little more complicated. First, a good illuminance meter is useful for this. Illuminance is a measurement of light that falls on or illuminates surfaces. Thus, while reading light off the screen would be a luminance measurement in nits or fL, measuring light directly from the projector's lamp would be an illuminance reading in Lux. Front projectors are about 1/3 the brightness of a typical flat panel, thus the black level measured off the screen is very low. Unless you have an expensive luminance meter, such as the Konica Minolta LS-100 which can accurately measure very low luminance, you may get more accurate readings by taking an illuminance reading directly from the lamp. The AEMC meter cited at the beginning of this tutorial is a good choice.

Just place the meter against the screen facing the projector's lamp and read a 100% output pattern in Lux. Then divide the Lux by 10.76 and multiply by the real* gain of the screen to get the fL for the projector. To get the lumens of the projector's lamp, just multiply the lux by the screen area in square feet and then divide by 10.76.

* Note: a screen's real gain will often be lower than its advertised gain. Manufacturers routinely inflate a screen's gain rating. Stewart is the only company I know of whose gain ratings are reasonably accurate.

ΔE Color Difference

The purpose of ΔE (dE or Delta-E) is to provide a single number that we can use to grade color accuracy relative to some standard. The smaller the number, the more accurate the color. ΔE can be used for both gray scale and primary/secondary color evaluation.

ΔE is based on one of two color appearance models, Luv or Lab. Both of these models were adopted by CIE in 1976 and they yield slightly different results. Luv numbers scale a little higher and place a greater emphasis on red, while Lab numbers place a greater emphasis on blue. In 1976 when CIE was considering the adoption of a color appearance model that offered a more perceptually uniform standard, CIE had originally wanted to adopt Lab only, but the industries that CIE represents argued against a Lab only solution. They were concerned by the fact that Lab fails to offer a linear chromaticity diagram. For this reason, historically most video ΔE values have been expressed in Luv (which does offer a linear chromaticity diagram in u'v' units). However, since 1976 most of the research on the CIE system has relied on Lab only.

In 1994 CIE adopted another even more perceptually uniform standard--based exclusively on Lab--that is referred to as CIE94. It scales much smaller and reduces somewhat the 1976 Lab emphasis on blue. It also offers an easy analysis of the Chroma, Hue, and Lightness components of color error that can be useful. Finally, the CIE94 formula treats lightness very differently than the 1976 color difference equations. Both Lab and Luv 1976 models predict that you can substantially reduce perceived color error caused by oversaturation by simply lowering the lightness of the oversaturated color. According to the CIE94 formula, lowered lightness does NOT mitigate the effect of oversatuturated color. Rather, it just makes the color appear darker. So, which is correct? To my eyes the CIE94 model gets it right, but there are many in video industry that continue to rely on CIELUV.

Since 1994, there has been much additional work, and in 2000 CIE adopted yet another ΔE model, known as CIEDE2000, but it is a VERY complicated formula and has not been widely adopted outside of the textile industry. Future work points to a new universal standard, the latest version of which is CIECAM02. However, a color difference formula for CIECAM02 has not been officially endorsed by the CIE. So, for now, we are probably best served by the original 1976 and 1994 models, with the 1976 Luv model continuing to be the most popularly cited (though not necessarily the best) standard for video applications. I use CIE94 for all dE reporting, but to a large extent this is a matter of personal preference.

I provide a spreadsheet at the bottom of this tutorial that allows you to calculate CIELUV, CIELAB, or CIE94 ΔE values using SMPTE-C or Rec. 709 values against your own test data.

So, how do we measure color performance?

For years the most popular method of specifying the color of white has been in terms of color temperature, with 6500K being the spec for neutral white. In recent years, the inadequacy of this approach has become evident. The great weakness of color temperature as a specification of the color of white is that it assesses only the relative strength of red and blue—reddish whites yield a lower color temperature and bluish whites yield a higher color temperature. This ignores green altogether, which means that a very greenish white or magenta white could both be 6500K. Furthermore, color temperature is useless in any case when assessing the accuracy of primary and secondary colors.

ΔE offers a much better approach. SMPTE has established a standard for the color accuracy of Digital Cinema, which is 4 Lab (1976) units or less. (This is approximately equivalent to 1.5 CIE94 units for color.) This seems like a reasonable tolerance. Unfortunately, we are left with the problem discussed above: which ΔE standard are we to use? SMPTE offers no guidance as to why they selected CIELAB.

Consider this oversaturated, but dim, shade of green:

x0.296, y0.678, Y0.535

How far from the Rec. 709 standard does this green deviate? Using ΔE as a guide it is very hard to say. CIELUV reports that this green has a ΔE of 11.4, which, though far from perfect at just under three times the allowed color error, is not too bad. However, CIE94 reports that the same green exhibits a 1994 ΔE of 11.2, which is over seven times the allowed color error. This is a huge error. Two ΔE systems report radically different results for the same color!

Thus, although ΔE remains a very useful tool, it is probably wise to supplement it with a more objective measurement of color error. I believe that the best available is simply % deviation from specification. Using this standard, we can add to our ΔE number that relative to the Rec. 709 standard the green above is:

Lightness: -10.9%
Saturation: + 17.3%
Hue: +0.1%

Add to this the requirement that no color should exceed +- 2% error in lightness, saturation, or hue. Even this method is not perfect. The human eye is not equally sensitive to lightness, saturation, and hue errors, nor is it equally sensitive to errors in each of the primary and secondary colors. For example, red errors are much more easily noticed than blue errors. ΔE tries to accommodate these factors, but as we have seen the different ΔE formulas yield different results.

Test Patterns
I provided a download link at the end of this post for a file from which you can create a calibration DVD with all of the necessary test patterns discussed here. There are two important rules to keep in mind.
1. When you use color and white test patterns, ensure that they are the same level of stimulus. For example, use 75% white test patterns with 75% color patterns and 100% white test patterns with 100% color test patterns. The same rule applies to windows and full fields. Use one or the other. Don't mix and match.
2. Use window test patterns only for CRT and plasma. For everything else, you can use either one.

Setting White Level (Contrast)

The Contrast control determines the peak output your display will provide. Set too low you lose image punch and lower contrast ratios. Set this too high and you lose color accuracy and detail in bright scenes and you may suffer from eye strain.

The standard method for setting Contrast requires that you look at a test pattern that has a just-below-white stripe against a white background. You are supposed to set Contrast as high as you can without losing the ability to distinguish the just-below-white stripe from full white. I included such a pattern on the calibration DVD.

However, there are a couple of problems with this method.

Some displays, especially LCDs, will never suffer from loss of high level detail even with Contrast set to 100%. This method will recommend a setting that is much too high.
This method does not take into consideration color performance. Many displays will lose their ability to track a neutral white at high output levels with Contrast set as high as this method recommends.

Thus, I think that a better method for setting Contrast is to just set it at a level consistent with good color performance and reasonable light output for a given display device. What's a reasonable level?

CRT tubes: 30-40 fL
Plasma: 30-40 fL
LCD flat panel: 30-40 fL
Digital rear projection: 30-40 fL
Digital front projection: 12-16 fL


Setting Black Level (Brightness)

The typical method for setting black level is to use a pluge pattern that displays just above and just below black information against a black background. You set brightness so that the just-above-black is barely visible and the just-below-black is invisible.

However, if you have calibration equipment there is a less subjective method for setting brightness.

Set the contrast as described above and then measure and record the Y (luminance) of a 100% white test pattern.
Display a standard pluge pattern and set brightness by eye as best you can. You may find that it is hard to distinguish between one or two ticks on the brightness control by eye alone. If so, continue to the next step.
Display a 10% test pattern.
Adjust the Brightness setting so that this test pattern measures as close as possible to 0.6% of the Y (luminance) of the 100% white window. This sets your gamma at 2.22 for the the 10% stimulus level. In the great majority of cases this will be the correct setting for Brightness.
IF this adjustment falls within the one or two tick range you arrived at by eye alone, then this is the correct setting. If not, then leave brightness where it was using the purely subjective method. In short, use the objective method to refine the subjective method, but the subjective method defines the range of possible adjustments and that range should be VERY small.

Note: Since I originally wrote this, the AVSHD disc has released a very advanced version of the pluge pattern that allows the user to set black level with perfect accuracy by eye alone. If you have access to this disc, then use it. Because it is so precise, it makes using objective measurements to set brightness unnecessary.

There is one problem with the method just described. How do we set black level for broadcast sources where no test pattern is available? Fortunately, there is one approach that will get a correct black level even without a test pattern, but you must have a recorded source of broadcast material, either from a DVR or DVD.

Record a television source that includes a "fade to black" sequence that typically occurs in between commercials or between commercials and network programming.
Play back the sequence and pause at the "fade to black" section.
Using a colorimeter or a light meter, measure the light output of the black screen.
Adjust the black level up and down. You will find a place where additional adjustments of the Brightness setting will not affect the light output of the panel. That point just where the panel's light output becomes responsive to increases or decreases in the Brightness setting is the correct setting.

*Gamma is primarily a choice about shadow detail vs. darkness of blacks. A 2.5 gamma will give a higher contrast ratio and deeper blacks, but it will also reveal less information in dark scenes. I recommend a gamma in the 2.2-2.35 range.

Setting Sharpness

This one is simple. Just use the sharpness pattern to look for ringing or faint outlines along the edges of the horizontal and vertical lines in the test pattern. Set the Sharpness control to the highest point you can that minimizes ringing (you may not be able to eliminate it entirely). On some sets, the sharpness should be set to zero. But for most it is usually at about the 1/3 point. I include a test pattern for setting sharpness on the calibration DVD.

Setting Color/Tint

The standard method for doing this involves looking at a SMPTE color bar test pattern through a blue filter. This method has 2 drawbacks. First, at best it is an approximation of the correct setting. Second, and more importantly, for some displays it simply does NOT work. On some plasmas in particular I have noticed that this method will recommend a grossly inaccurate setting. Here's a foolproof method for setting Color/Tint that does not use filters.

Color

Point the colorimeter or light meter towards the screen and display a 100% white test pattern.
Measure the Y value (luminance) of white.
Display a 100% Red test pattern, and measure the Y value here as well.
You will notice that as you move the Color control up and down, the Y value of Red increases and decreases, but white stays the same.
Set the color control at the point where Red measures closest to 21% of the white reading.

Note: It is not really important whether you use 75% or 100% patterns in this test, so long as you use the SAME level of intensity for both.

Tint

If you have not already done so, adjust the gray scale and get it as close to D65 (x=0.3127, y=0.329) across the entire range as possible.
Point the colorimeter towards the screen and display a cyan test pattern.
Put the Tint control at its neutral mid setting.
Use the software controls to plot cyan on a CIE chart.
Adjust Tint up or down until the reading places the hue of cyan as close to the target on the CIE chart as possible (it is useful if the software has a continuous reading mode, so you can see changes you make to Tint in real time).
If you had to substantially adjust Tint from the neutral point to get an accurate hue of cyan, then check the other secondaries. You may have to select another setting that gets all 3 secondaries as close to correct hues as possible.

Adjusting the gray scale

Briefly, gray scale adjustment simply involves adjusting specialized controls that allow a display to track a neutral shade of white throughout its entire range from the blackest black to the whitest white.

Unlike a good CMS, which is rare, virtually all displays have gray scale controls. Sometimes they are in the user menu, but often they are buried in a service menu that can only be accessed by a specific key sequence on the remote. The goal is to get an xy measurement as close as possible of 0.3127/0.329. The calibration software will provide these raw numbers and some type of graphical representation of RGB balance relative to the target gamut. Ideally, you woukld like to see red, green, and blue all balanced equally at 100%. That is the definition of neutral white for the selected gamut.

To calibrate the gray scale:

Aim the meter at the display.
Select a 80% stimulus window on the calibration DVD.
Adjust the RGB Contrast controls until RGB is balanced at 100% or until you read x0.3127, y0.329.
Select a 20% stimulus window from the calibration DVD and use the RGB Brightness controls to balance RGB at 100% or achieve x0.3127, y0.329.
Repeat the last two steps as many times as necessary until both the 80% stimulus window and the 20% stimulus window measure neutral gray. This may take several sets of measurements.
Finally, take an entire series of gray scale measurements at 10% intervals from black to 100% to ensure that the display tracks gray accurately throughout the entire range.

Sometimes you may find that even though 80 and 20% stimulus are neutral gray, the mid range 40-60% stimulus is not. This means that your display won't track a good gray scale and you have to make some compromises. The general rule of thumb is to focus on getting the mid range to track neutral gray. Then get the low end right. Sacrifice accuracy at the top end if you have to.

Note: There is no industry-wide accepted terminology for gray scale controls. You may see RGB Contrast/Brightness, RGB Gain/Bias, RGB Gain/Offset, RGB Drives/Cuts. They all mean the same thing. Contrast, Gains, and Drives are for adjusting the bright end of the gray scale. Brightness, Biases, Offsets, and Cuts are for adjusting the dark end of the gray scale.

Adjusting Color using a Color Management System (CMS)

Point your colorimeter towards the screen and display a white test pattern, and then take a reading.
Display a red test pattern AT THE LEVEL OF STIMULUS AS THE WHITE TEST PATTERN, and then take another reading.
Repeat the previous step until you have measured all of the primary and secondary colors.
Use the software controls to plot the Lightness, Saturation, and Hue of all of the colors.
Adjust these values for each of the colors, one by one, using the CMS until Lightness, Saturation, and Hue line up as close as possible to the references for your target gamut (see those references above). It is helpful if the software has a continuous reading mode so your changes can be viewed in real time.

Note 1: You probably won't be able to get all colors lined up perfectly, but get them as close as you can.

Note 2: Some software only plots changes that are visible on the CIE chart. This allows you to get saturation and hue right, but it doesn't tell you how your changes affect the brightness of the colors. Unfortunately, some CMSs automatically change the brightness of a color as you adjust its saturation. This will give you a good looking CIE chart, but you could actually end up with LESS accurate color than when you began.

Note3: The human eye is not equally sensitive to all colors and all color differences. For example, it is more important to get red and green right than blue. It is also more important to get correct hues than correct saturation.

Adjusting Gamma

First, it is important to understand that not all displays even offer the controls to directly calibrate gamma (Panasonic plasmas, for example). Having said that, there are several ways to change a display's gamma response.


First, ensure that you have already calibrated white level, black level, and the grayscale. These steps alone can often get you a long way towards a good gamma response.
Experiment with different picture presets. Use the preset that offers the best gamma response. "Best" is defined as the flattest response within a range of 2.2-2.35.
Experiment with different gamma presets. Some displays offer a gamma selector that is independent of the picture preset. Just select the one that offers the best response.
Best of all, a very few displays will allow you to directly calibrate gamma by changing the output at each level of stimulus. Again, select a value at each level that results in the best gamma response.

That's it. Now you should go back and remeasure the white/black levels, grayscale, and color gamut. There may have been interaction between the various adjustments and you may have to go through two or three rounds of measurements until all are correct.

Calibration DVD

I have created a very simple calibration DVD that has all of the test patterns you will need. I have tested it against other well-known discs for quality control. You may download and use it free of charge. The disc includes:

11-point grayscale in windows and fields
Alternating 80/20% windows and fields for initial grayscale adjustment
75% RGBCYM patterns in windows and fields
Just-below-white pattern for setting Contrast and a just-above-black pattern for setting Brightness
Window and field test patterns for checking gamma.
A test pattern for checking sharpness.

You navigate through the individual patterns by pressing the Chapter Forward button.

I have provided the necessary DVD files in 2 formats:

For those who have Nero, you can download a zipped *.nrg image file. After downloading and extracting to your hard drive, just double-click the file and it will open in the Nero Burning ROM.
I also provided zipped generic DVD files. After downloading and extracting to your hard drive, you can use DVD Shrink and DVD Decrypter freeware (or many other programs) to burn them to disc.

After zipping, these files are only a little more than 1-megabyte, so it is an easy download.

Download Nero image (http://displaycalibrationonline.com/dvd/nero/dvd_calibration_new.zip)
Download generic DVD files (http://displaycalibrationonline.com/dvd/generic/dvd_files.zip)
Download Nero image in PAL format (http://displaycalibrationonline.com/dvd/nero/dvd_calibrationPAL_new.zip)

What you also need

All displays include adjustments for Color, Tint, Brightness, Contrast, and Sharpness. You can use test patterns from calibration DVDs to correctly adjust these parameters. However, to calibrate a display you must go beyond these basic adjustments and that requires two additional items:

Calibration equipment, which I discuss at the beginning of this article.
A display that has controls that go beyond the basic user adjustments listed above. This is the single biggest impediment to getting a good calibration. Most displays simply lack the controls necessary to calibrate them fully.

In addition to the basic user controls, most displays have gray scale controls, though they are often hidden in the service menu and sometimes labeled with obscure nomenclature. Sometimes manufacturers offer even less. Some modern displays--the JVC RS1 comes to mind--have grayscale controls that are easily identifiable and accessible in the user menu, but which adjust the entire range of the gray scale at once, rather than offering separate controls for darker and lighter shades of gray.

Color decoding and the resulting color gamut errors are routine among modern displays and the great majority lack controls to adjust these critical parameters correctly. Thus, before you consider whether you want to get your display calibrated, you should first ensure that it CAN be properly calibrated with the controls it offers. Many, perhaps even most, cannot.

With this in mind, I thought it would be useful to maintain a database of displays that include a full compliment of calibration controls. At a minimum this includes independent control over the bright and dark ends of the gray scale, and at least one of the following:
- color decoding controls
- a full-featured 3-axis CMS for all primary and secondary colors

If you have a full-featured CMS, then you don't need color decoding controls.

If anyone knows of additional displays, I'll add them to the list.

Front Projection

JVC RS20/25/35
Planar PD 8150
Samsung SP-A800/900
Sharp XV-Z20000 (DLP)
Epson Home Cinema 1080 UB/6100/6500UB/7100/7500UB/9100/9500 (LCD)
BenQ W9000/10000/20000 (DLP)

Rear Projection

Mitsubishi 1080P Diamond Models (DLP/LCD)*
Samsung (DLP)

Flat Panel


Samsung PNxxA550 and up plasmas
Samsung PNxxB650 and up plasmas
Samsung LNxxA550 and up LCDs
Samsung LNxxB6/750 LCDs
Samsung UN55B6/7/8000 LCDs

* Includes adjustments for color decoding and hue in the user menu, but saturation can be adjusted only in the service menu.

Cool, thanks for the step by step. I can't wait to try these method. I have always found it difficult to use the blue filter to adjust the color and tint.

Excellent.
Thanks for writing this up Tom.

Can you address the rationale behind using "window" patterns for non direct-view displays?

Can you address the rationale behind using "window" patterns for non direct-view displays?Some types of displays, CRTs and plasmas come to mind, lose the ability to reproduce higher levels of output across the whole screen as increased voltage is applied. You can get around this problem by using a test pattern in which the gray levels are reproduced in relatively small windows, rather than the full screen.

For other types of displays this is not really a problem. However, since it is absolutely required for some direct views, it was just simpler to describe a single procedure. Also, relatively small gray windows throw less light into the room than full screens of gray, lessening the possibility that room reflections may contaminate the readings.

Color Definitions (HD)
-------------x--------y-------Y
White--------0.313---0.329---1.00
Red----------0.640---0.330---0.213
Green--------0.300---0.600---0.715
Blue----------0.150---0.060---0.072
Cyan---------0.225---0.329---0.787
Magenta------0.321---0.154---0.285
Yellow--------0.419---0.505---0.928


What about Color Definitions for SD (Rec 601)? I can get xy from HCFR but not Y. Adjusting for SD would have some different percentages wouldn't it? Are the Y's the same for HD and SD?

Thanks.

I found this:

Rec. 601 (SMPTE C) for 480i, 480p

White (D65) = 0.3127, 0.3290
Red = 0.630, 0.340
Green = 0.310, 0.595
Blue = 0.155, 0.070
Yellow = 0.421, 0.507
Cyan = 0.231, 0.326
Magenta = 0.314, 0.161

but I am still missing Y.

SMPTE-C Y
White 1.00
Red 0.212
Green 0.701
Blue 0.087
Cyan 0.788
Yellow 0.914
Magenta 0.299

Thanks, Tom. You rock!! So the percentages would basically be the same for SD and HD, correct?

Really nice guide Tom, I have one question.


Set the color control at the point where Red measures closest to 21% of the white reading.


Why do you use the saturation control to set Y to spec instead of setting x,y to spec? My display's saturation control changes the spectral distribution of the primary so I use it to set red at the Rec709 x,y point. In other words is the perceived result of deltaY=0 better than deltax=deltay=0?

thanks

Why do you use the saturation control to set Y to spec instead of setting x,y to spec? My display's saturation control changes the spectral distribution of the primary so I use it to set red at the Rec709 x,y point. In other words is the perceived result of deltaY=0 better than deltax=deltay=0?Zoyd, this is something that may vary among displays. However, in my experience, the main Color control primarily affects color luminance and only secondarily saturation.

Zoyd, this is something that may vary among displays. However, in my experience, the main Color control primarily affects color luminance and only secondarily saturation.

I'm not sure how one would determine primary vs. secondary effects when using a color control since the two are coupled. Using the i1pro in spectrum view I can see both things happening and on my display, the spectral shape changes in the wings and the intensity changes. Here is a plot using a green pattern;

http://i64.photobucket.com/albums/h173/prairie_2006/specomp.png

Note that the % change in the red and blue side peaks are much greater than the change in the green peak.

The before and after green coordinates are:

Color=-5
.281
.583
36.9

Color=5
.269
.656
42.9

So there was a 4% change in x, 12.5% change in y, and 16% change in Y. I guess the real question is what is the deltaE with respect to Rec709 in an appropriate perceptual colorspace that includes luminance as well as chroma.

zoyd

check out the front projector forum - Hugh2/hughman did that very study of changes to color control impact on the CIELCH measures (same dE as CIELUV) of his JVC - but it is rumoured the firmware version may behave slightly different. I would say it is generally the case that you have to shift color brightness significantly before color saturation moves with video color controls - he posted several sets of numbers on that starting here....

http://www.avsforum.com/avs-vb/showthread.php?p=10426396&&#post10426396

I have observed similar with Sony Ruby/Pearl - the dL hit to move in the primaries with the color control per spec resulted in much worse dE than leaving primaries be and only shorting dL a bit under spec.

Of course Tom's post was how to use a CMS and video decoder that is capable of getting you the perfect result - as his other posts on color demonstrate - sometimes this can be an exercise in futility in picking the worst vs. best compromises.

The only thing I would add is to repeat the measures with 100% patterns - as sometimes displays can have settings impacting bright colors like DLP's BrilliantColor(tm) or any dynamic iris - which maybe can be turned off - but if not - compromise between light/dark colors time!

Also if doing tint with this method of sensoring rather than filtering - I would do it after greyscale not before - because secondaries shift with greyscale - with filters this is irrelevant because you have bluescale not greyscale!

Using red brightness to set color levels will only work if your set has no red push - if it does then the color will probably be too low overall - so again measure blue/green levels to find the compromise in between.

I also use 100% white for greyscale to first establish my clipping limits - I find hot white colortemp blowouts much more annoying than the tweak to contrast they give.

Great thread, thanks for the link. If I understand your comments regarding dL at different luminance levels it means the perceptual errors are actually a function of where you are in the luminance curve, is that correct? If so then optimizing dE or (dL,dC,dH) will depend on this too.

I can see both things happening and on my displayAs I said, this may vary among displays. In any case, using a ratio of white/red Y is a very easy and accurate way to set Color properly, certainly better than using a filter and a SMPTE color bar, which was my only point.

I previously did some formal measurements on 2 displays.
http://www.avsforum.com/avs-vb/showthread.php?p=10214658&&#post10214658
http://www.avsforum.com/avs-vb/showthread.php?p=10221787&&#post10221787

As I said, this may vary among displays. In any case, using a ratio of white/red Y is a very easy and accurate way to set Color properly, certainly better than using a filter and a SMPTE color bar, which was my only point.


yes, I agree it's superior to the filter method but as always I'm interested in squeezing dE as much as possible. I repeated your red test from those links and I see similar behavior on my display but not quite as severe a hit in Y to get my red primary aligned to rec709. At color=-2 Yred=0.21*Ywhite, at color=-5 I get alignment in x,y and Yred is 18% low.

As for dE(LCH), here are the results for my display:

color=-2 (Yred=0.21*Ywhite), dE=8
color=-3 dE=4.4
color=-4 dE=5.7
color=-5 (aligned to CIE,Yred=0.17*Ywhite) dE=12.4

This agrees with krasmuzik's comment about shorting the color brightness slightly to get the best perceptual results(assuming you're starting from outside the triangle). I was also surprised to see that dE was such a strong function of L*

Great thread, thanks for the link. If I understand your comments regarding dL at different luminance levels it means the perceptual errors are actually a function of where you are in the luminance curve, is that correct? If so then optimizing dE or (dL,dC,dH) will depend on this too.

That depends on what white reference you used - if you used 100% as your white reference then yes for anything less - dE models perception that color error perception is greatly dependent on relative luminance.

You could also use the same white reference as your color bars - make everything 75%. Then it tells you what errors you see in the color bars since you adapt to its white as your reference.

But if you wanted to quickly compare 100% colorbars to 75% colorbars - now 100% white becomes your reference - and the 100% colorbars will appear to have the worst errors.

Literally it is all a matter of perception. When I plot dE for greyscale I could go eitherway. If I look at a grayscale chart I cannot see near black color deviations, however if I look at grayfields sequentially and adapt my eye to near black (making it my "white" reference) - then I can see the errors.

The perceptual model does not consider night blindness - so obviously there is a limit you can see color error.

I am trying to get to rec601 (just 480p dvd player)

100% stimulus values:
Yred = 4.64 divided by Ygray=23.005 I get 0.201

75% stimulus values:
Yred=2.543 divided by Ygray=9.543 I get 0.266

I adjusted the color down from +9 to -10 and got the following result for 75%
Yred=2.342 divided by Ygray=10.204 is 0.230

It appears I am headed in the right direction. It just seems like a lot of clicks down (for color) to get a slight change in the Y. I guess I should keep reducing the color until I get as close to 0.212, right?

I have also attached the plot of my luminance prior to any adjustment.

Any feedback would be helpful.

I was not sure if I should use the 75% or 100% for color adjustment. I used the 75% based on the guide.

It appears I am headed in the right direction. It just seems like a lot of clicks down (for color) to get a slight change in the Y. I guess I should keep reducing the color until I get as close to 0.212, right?Yes. Remember, though, you may have a color decoder error, so when Color is set good for Red it may be screwed up for Blue and/or Green.

There is absolutely no advantage to using 100% stimulus and it could potentially cause problems. Use 75%. That's why I included that in the instructions. Also, be sure to use a window, not a full screen. Finally, what type of display do you have?

Yes. Remember, though, you may have a color decoder error, so when Color is set good for Red it may be screwed up for Blue and/or Green.

There is absolutely no advantage to using 100% stimulus and it could potentially cause problems. Use 75%. That's why I included that in the instructions. Also, be sure to use a window, not a full screen. Finally, what type of display do you have?

My display is a DLP Front Projector (Benq PB6200). Using the Avia color decoder test - it appears that it has a bit of a red push. Will that give me some problems? Maybe I should use blue or green?

I thought it would be useful to maintain a database of displays that include a functional CMS.


I take it you don't consider the pioneer elite CMS functional. Does it allow for any improvement in color or is it just worthless?

Using the Avia color decoder test - it appears that it has a bit of a red push. Will that give me some problems?This display has no color decoder adjustment. In fact, it has no CMS. All you've got to work with is the Color control. If you have serious red push, then it's a trade-off. Getting red right, means you have to lower the intensity of B and G more than ideal. Find some compromise that's acceptable.

If you are interested in this stuff, you might consider investing in a display that offers more control over the image quality.

I take it you don't consider the pioneer elite CMS functional. Does it allow for any improvement in color or is it just worthless?I'd say worthless describes it pretty well. You can move the color points with it some, but it screws up the gray scale.

Hello Tom,
Most of this is still a bit beyond me, I really appreciate your posts. As for your data base on CMS displays, I have a Sanyo PLV-Z4 front PJ that allows color level, color phase and gamma. Do not have anything but DVE for calibrating so I do not know if these are truly functional, they do offer some change but, I cannot tell what they are effecting. Do you know what they mean by color phase?

This display has no color decoder adjustment. In fact, it has no CMS. All you've got to work with is the Color control. If you have serious red push, then it's a trade-off. Getting red right, means you have to lower the intensity of B and G more than ideal. Find some compromise that's acceptable.

I'll try to find a decent compromise. I would guess that I should measure 75% R, G, and B to see how close I am and then sort of try to split the difference? Using the tint to adjust cyan to the target is still something I need to do.

If you are interested in this stuff, you might consider investing in a display that offers more control over the image quality.

I am and you are right. Right now I am sort of 'tryin' to make a silk purse out of a cow's ear'. Just need to get the funds scraped together. I will say this, all you guys have certainly helped me to acheive much better image fidelty..... Sorry, I just like to say/write image fidelity - it's pretty cool!

Thanks again for the help.

Tom, you can add the Sharp XV-Z3000 and Sharp DT-500 to the CMS list. These doesn't however have user menu cuts for any color, and only has R and B drive. I assume full control is available via a service menu to cuts/drives.

Hello Tom,
Most of this is still a bit beyond me, I really appreciate your posts. As for your data base on CMS displays, I have a Sanyo PLV-Z4 front PJ that allows color level, color phase and gamma. Do not have anything but DVE for calibrating so I do not know if these are truly functional, they do offer some change but, I cannot tell what they are effecting. Do you know what they mean by color phase?

phase is tint/hue - and it has a very narrow range of adjustment.

You cannot reduce color saturation - and the color level is only good enough range to fix the displays red push - if your source has red push you are screwed. Also it only works on a narrow range of tints - so you fix red - then notice orange and crimson are still off. A true CMS does not work that way!

I call such budget systems color replacement systems - because you are adjusting colors that are nearby to colors that you frame grab from the video.
Their CMS gamma is wierd - I assume this is a gamma applied to that color in the video - but it already has a very wide ranging master gamma slider that is great - as well as a service menu with RGB gamma to fine tune when working on greyscale. So I don't really see what use it has.

Does the Panasonic's AE1000 or the Sanyo Z5 elevate onto this list?

Bill

I haven't seen either, but Kraz insists that the Sanyo is an ersatz CMS only with no real value. From reading about the Panasonic, it sounds very similar, but I'll I withhold judgment until I actually see one.

Bill

You need gamut testpattern to prove if it is a CMS or "CRS". AVIA PRO has a sequence, DisplaYMate calibration patterns - and most computer based calibration softwares show the CIE gamut - but you also need to run the tests at various brightness levels. A true CMS is redefining RGB gamut in all 3D - brightness, chroma (saturation) and hue - if they just replace those RGB - then they have not fixed the gamut as other colors are still screwed.

I had heard the Panny would fix that brightness level - but other brightness levels were still screwed - but no experience with it.

Randy Tomlinson has a review of the HLS Samsung DLP rear projector in this edition of UltimateAV that comments extensively on its CMS. It's worth the read.

http://www.guidetohometheater.com/rearprojectiontvs/507sam5688/

My only quibble is his insinuation that you simply can't do decent color correction without a $15,000 Photo Research spectroradiometer. Just silly.

The AE1000 has a functioning CMS. It has controls for Color, Tint and Brightness.

It has controls for Color, Tint and Brightness.This is not what we mean by a Color Management System. The NTSC specification requires ALL displays to have adjustments for Color, Tint, Sharpness, Brightness, and Contrast. A CMS goes significantly beyond this.

This agrees with krasmuzik's comment about shorting the color brightness slightly to get the best perceptual results(assuming you're starting from outside the triangle). I was also surprised to see that dE was such a strong function of L*
I missed this comment my first pass, but this is a point I tried to make a while ago here:
http://www.avsforum.com/avs-vb/showthread.php?p=6637132&&#post6637132

I have also posted a critique of the dE(u'v') method as going too far in the other direction, but that is for a different thread...

Bill

This is not what we mean by a Color Management System. The NTSC specification requires ALL displays to have adjustments for Color, Tint, Sharpness, Brightness, and Contrast. A CMS goes significantly beyond this.


For EACH COLOR :). (Sorry, I was a bit short there) One can store up to eight different colors per memory.

Tom,
The Optoma HD7100 has a full working saturation, tint and lightness adjustment per primary and secondary color. These adjustments are in the SM.
Despite all its adjustments, I do not seem to be able to get green to its theoretical x,y value in the gamut. Could this be a result of the grey screen I am using?
Any comments/suggestions?
Thanks a lot to you and all other contributors to this great thread.
Fermin

Hi Tom,

Excellent write-up!!

And since I finally had a couple of free hours last night I decided to calibrate my Sharp Z12 using your exact procedure outlined above. For the most part everything worked great. I was able to adjust color and tint as you outlined, and only had to make minor adjustments to color bias and gain in order to get the tracking under dE of 3 across the board (except for 0 IRE, which I know is below the effective range of the EyeOne Pro). Then I finished up the color decoding by adjusting green and blue...so far so good.

The only problem I ran into with the Sharp was when it came to adjusting the gamut - Green was a problem, and because of the green problem, cyan is not right either. I was able to move all of the other colors so that they are right on the CIE targets, but green is undersaturated (if I am interpreting the chart correctly - green was originally outside the triangle, but lower than the green coordinate and way to the right), so I have no way to correct it (and cyan is undersaturated as well). Despite that little problem, I double checked everything else a second time and the color decoding is very, very good, as is the grayscale tracking.

My subjective impression is that most colors look absolutely dead accurate, though the greens looks a bit "pale". This might be because I know that green is not quite right, or it just may be due to viewing oversaturated greens for so long - I really don't know, but either way I am EXTREMELY happy with the results and the CMS functions of the Sharp. It was a real pleasure to have that much control over color! :)

Many thanks again!

Bob:

This sounds like mainly a hue problem. First, put the green controls back to their default. Second, adjust green hue until the measured point falls on a line between the white point and the target green point. Finally, adjust green saturation (which will move the measured point closer to or further from the white point) until it falls on the target.

You should be able to adjust this out. I don't know what you mean when you say that "I have no way to correct it".

For EACH COLOR :). (Sorry, I was a bit short there) One can store up to eight different colors per memory.

That sounds like a color replacement system to me. You have to run the gamut tests to prove the entire gamut actually changes - not just one color.

A true color management system will do a 3x3 matrix transform to warp the gamut based on the editing of RGB parameters. Having a lookup table to remap a few colors is not at all the same thing.

Thanks, Tom, I'll give that a try tomorrow night (my next opportunity).
I don't know what you mean when you say that "I have no way to correct it".
Since I don't have a chart to post, I'll try my best to explain it. The green primary was initially located to the far right (like half way between green and red horizontally) and slightly lower (vertically) than the targeted primary. When I tried increasing saturation, there was no change in the reading at all, but when I lowered saturation the point dropped lower by quite a bit. When I tried adjusting hue in one direction I could move the point to the left, but the very left most I could get it was on a line between the green and red targets, which is where I left it. Cyan acted similarly in that it was inside the triangle initially, and no amount of change would allow me to place cyan on the line between green and blue - it was and is still inside of the triangle. These observations were confirmed visually as I watched the 75% green and cyan windows from the Accupel. Green looks "pale" for lack of a better term and I could not get it to look any "greener".

I started with 6500k as a starting point. Maybe I will try measuring a few other temperatures to see if there is a better starting point for calibration. I'll also double check to see if I did something stupid in feeding the signal from the Accupel to the 12K's DVI input, especially since you got better results than I did.

Thanks again for all of your help!

I'll also double check to see if I did something stupid in feeding the signal from the Accupel to the 12K's DVI input, especially since you got better results than I did.I think that's your best bet. The Accupel has so many settings for color space and phase, it's easy to pick one that doesn't work well with a given display.

What you describe just doesn't sound right to me. Either it's a measurement anomaly or the PJ is defective in some way.

The simplest way to do with would be with a test DVD. GetGray has some great patterns for this.

Despite all its adjustments, I do not seem to be able to get green to its theoretical x,y value in the gamut. Could this be a result of the grey screen I am using?I doubt it. My guess is that the degree is error is larger than the range of adjustment.

See your PM.

That sounds like a color replacement system to me. You have to run the gamut tests to prove the entire gamut actually changes - not just one color.

I have, and it's easy to move all colors into rec.709 coordinates.

Before CMS:

http://i176.photobucket.com/albums/w192/anbjornk/PT-AE1000withoutCMS.jpg

After CMS:

http://i176.photobucket.com/albums/w192/anbjornk/PT-AE1000withCMS.jpg

I think that Kraz's point, though he can speak for himself, is that a spot color replacement tool could achieve the result you show above by just using the primary and secondary colors as the targeted colors. However, it would not have changed the PJ's fundamental ability to render ALL color. A symptom of this is that it would have changed red, for example, but left orange unchanged.

The reason I'm suspicious that it's a color replacement tool and not a true CMS is that it allows the user to select up to 8 colors at random to adjust, rather than offering the primaries/secondaries as the only pre-defined alternatives, but I could be wrong.

Kraz, maybe you can explain how the gamut test works. I ran it. It gives a very long series of colors based on RGB combinations. I really don't see how to use this without knowing what the xy values of the colors are supposed to be.

Tom are you talking about AVIA PRO's? There is a checkerboard display version of it that it is designed to be viewed on a PbPr component difference (or maybe was NTSC IQ?) vectorscope as grid. But knowing the target display is SMPTE-C and the DVD coding is REC601 you could do the matrix math to derive the xy from the geometry math for a regular stepped grid on a vectorscope (yes had they documented it would have been useful - one of these days I will write a MatLab program to figure the numbers out - Maybe Bill has some free time to R&D a CalMan gamut tester synced to AVIA PRO!). You are on the sequential version you step thru with window fields for making measures. But you can visually use the checkerboard version just to see what colors the adjustments impact. If you can't find it I will look up the menu path.

Certainly DisplayMate full gamut pattern http://www.displaymate.com/dwsct.html or any softwares full color CIE chart http://www.colorvision.com/images/ColorFacts/CFInstrumentCIE2.jpg is easier to see the results of color editing than making tedious measures. These smaller snaps may be hard to see - but those with these software should try it with the charts full screen.

anbjornk

Does editing red shift ALL colors with the red component - or like the Sanyo does it only shift a very narrow range of Red?. The Sanyo also has only enough framegrabber slots to get primaries, secondaries, and maybe a couple flesh tones. But look at the full color gamuts and you still see slivers of uncorrected colors.

I only see seven colors (RGBCMYW) on that CIE chart - and you have only x,y and thus missing Y data - which means it is very possible you compromised color brightness trying to get color gamut correct. But unless you look at a full color pattern - you cannot even prove that you fixed the gamut - you may have just fixed seven colors in it. The point is that while a CRS can remap any very limited set of colors - with a CMS you are editing the very locations of the RGB primaries the display produces to warp ALL of the colors - and some even further warp the secondaries.

Obviously it becomes crazy to measure orange, crimson, brick red, flesh tones, etc - so I am just saying just look at charts that have the full range of colors and play with the controls.

I think that Kraz's point, though he can speak for himself, is that a spot color replacement tool could achieve the result you show above by just using the primary and secondary colors as the targeted colors. However, it would not have changed the PJ's fundamental ability to render ALL color. A symptom of this is that it would have changed red, for example, but left orange unchanged.

The reason I'm suspicious that it's a color replacement tool and not a true CMS is that it allows the user to select up to 8 colors at random to adjust, rather than offering the primaries/secondaries as the only pre-defined alternatives, but I could be wrong.


Does editing red shift ALL colors with the red component - or like the Sanyo does it only shift a very narrow range of Red?. The Sanyo also has only enough framegrabber slots to get primaries, secondaries, and maybe a couple flesh tones. But look at the full color gamuts and you still see slivers of uncorrected colors.


Actually, even though green supposedly has moved quite a lot in the CIE chart, I cant't actually see the difference in videomaterial. The shire in LOTR looks all the same. The only obvious change is in red/orange, where orange has been less orange. This can be seen easily on leloo's hair in the fifth element.

Btw. I used only the color and tint adjustments, and left brightness alone.

I think you guys are correct, it's a CRS rather than CMS.

This is why CIE L*u*v* is a better colorspace than xyY - green hues are not as easy to see as red and blue, even in video with green being brighter than red and blue! Whereas on your xyY chart you can barely even see the hue is off on red even though your eye could see it was too orange.

I can back up what Bob is saying about the greens on the 12k. I had the same exact experience.

Rob

I'm reasonably confident that after proper calibration one can get the Sharp 12K's colors very accurate. This confidence is based on 2 factors. First, the published reviews of the 12K are pretty consistent about its color performance. Second, my own experience with the 20K.

Here's WSR's measurement pre-calibration.

http://home.comcast.net/~tlhuffman/cms/before.gif

Post-calibration

http://home.comcast.net/~tlhuffman/cms/after.gif

This requires a little imagination, because unfortunately Greg Rogers choose this review to switch color spaces from xy to u'v' in midstream.

Here's HTM's measurement before calibration

http://home.comcast.net/~tlhuffman/cms/htm_before.gif

Unfortunately, they don't provide an after but I'd be very surprised if this level of error was uncorrectable for the Sharp CMS. The main problem seems to be that green is too yellow.

I can report first hand that the 20K is capable of essentially perfect green.

Here's the HCFR file with the Spyder2. While the red is purposely off the mark, the green and the blue could not be adjusted exactly to the standards. No matter what I did, I could not get the green any further to the left, without moving it significantly towards white. I got very similar results from the Xrite DTP-94, although the green was slightly closer.

Rob

I doubt it. My guess is that the degree is error is larger than the range of adjustment.

See your PM.

Tom,
The attached gamuts are the before and after CMS. The default on saturation is 0 at its maximum. Green tint will move the green position into the triangle, under the green reference point. I don’t know what can be done, if anything, to get the green color in its ideal place.
Readings made from the screen.
Any suggestions?
Anybody?
Thanks.
Fermin

Tom, first of all great thread and thanks for the tips! In the EMP-TW1000 thread you showed a post calibration chart. I am now going through and calibrating my Epson 1080 and if possible could you post or pm your settings to me to use as a reference so I can see how they compare. I known mine will be somewhat different.

Thanks !!!

Here's the HCFR file with the Spyder2. While the red is purposely off the mark, the green and the blue could not be adjusted exactly to the standards. No matter what I did, I could not get the green any further to the left, without moving it significantly towards white. I got very similar results from the Xrite DTP-94, although the green was slightly closer.A couple of things. First, don't use the Spyder2 for this stuff. It really isn't accurate enough to provide numbers you can rely on. Second, what your numbers show is performance almost identical to the published results. The DTP-94 would have been even better. Here's what your calibration showed.

http://home.comcast.net/~tlhuffman/cms/12k.gif

This is actually quite good. Bob Sorel's results were MUCH worse than this. There's something else going on in his case.

I'd be more concerned about the oversaturated red than the slightly yellow green. BTW, I really wish people would attach or post image files so everyone could see them, rather than HCFR calibration files.

Tom: thanks for your explanation and process.

One thing that I have been wondering - when altering the grayscale cuts/gains for each of the primaries, does changing each of the 6 controls have varying effects on the resulting x,y,Y numbers? And do these vary by display type/manufacturer/model?

I've been using the Spyder Platinum with the Ruby and CalMAN. Been a bit of shooting in the dark. I'm trying to get a better handle on what's happening as I apply changes, so I do this in a more intelligent manner. I've found that I can go down the wrong path with changing things (too much in one direction or another and impacting more distant IRE stimulus areas). Your approach of picking 30% and 90% works well. It's when I'm trying to move down to 20% -> 10% that I get into trouble (I won't even bother with 0% since I don't think the Spyder's up to it).

Any help would be appreciated.

Here's the gamut of the 12k with the DTP94. These are the same settings from the Spyder, that are shown in post #54 above. They are almost identical except for the green (and subsequently, the cyan), which measures worse. As with the Spyder, I could not get the green anymore to the left without moving in towards white. Considering these two graphs, I'd say the Spyder is a worthy contender considering how inexpensive it is. It's not perfect, but neither am I.

Rob

Sorry, here it is. See, I told you I wasn't perfect.

Rob

Robbyc30, assuming that the white lines in your above graph are the measured values, then your gamut looks almost exactly like mine. Mine just looks worse because the the graph is larger and easier to read...:)

Here's the gamut of the 12k with the DTP94. These are the same settings from the Spyder, that are shown in post #54 above. They are almost identical except for the green (and subsequently, the cyan), which measures worse. As with the Spyder, I could not get the green anymore to the left without moving in towards white. Considering these two graphs, I'd say the Spyder is a worthy contender considering how inexpensive it is.That's actually not such a small difference, but a pretty significant one. Now your color measurements are beginning to look a lot more like Bob Sorel's. It's the difference between what I would consider an acceptable deviation to an unacceptable one.

One thing that I have been wondering - when altering the grayscale cuts/gains for each of the primaries, does changing each of the 6 controls have varying effects on the resulting x,y,Y numbers? And do these vary by display type/manufacturer/model?It can, and yes.

I've been using the Spyder Platinum with the Ruby and CalMAN. Been a bit of shooting in the dark. I'm trying to get a better handle on what's happening as I apply changes, so I do this in a more intelligent manner. I've found that I can go down the wrong path with changing things (too much in one direction or another and impacting more distant IRE stimulus areas). Your approach of picking 30% and 90% works well. It's when I'm trying to move down to 20% -> 10% that I get into trouble (I won't even bother with 0% since I don't think the Spyder's up to it).

Any help would be appreciated.I don't know that you need help. It sounds like you are doing just fine. Meters often start to lose accuracy below 30 IRE, especially if you are taking readings off the screen, so I wouldn't worry about that too much. See your PM.

So, is there something wrong with Bob's and my 12k? Is it possible my greyscale settings are affecting the gamut? My green gain is all the way down, at -30, twice as far as the red and blue. For the offsets, green and blue are in the -10 area, and red is -5. I can't see how I could raise the green gain much because if I raise the red gain, the high-mid IREs start getting pink. I have ordered another 12k because of a large, bright, sometimes flickering, hotspot just right of center screen. The new one should be here on Tuesday. I will report back if it has the same green problem.

Rob

So, is there something wrong with Bob's and my 12k? Is it possible my greyscale settings are affecting the gamut?It's possible. With the unit set at 6500K, you shouldn't have to adjust the RGB gray scale controls that much. You might want to check the gamut of the new unit before/after making any gray scale adjustments.

This is why CIE L*u*v* is a better colorspace than xyY - green hues are not as easy to see as red and blue, even in video with green being brighter than red and blue! Whereas on your xyY chart you can barely even see the hue is off on red even though your eye could see it was too orange.


I agree ! It's easy to spot the the differences the CMS/CRS system made when displaying 75% colorbars (I used 75% windows when setting the colors in the AE1000's CMS), but not with other color intensity levels.

anbjornk

Did you measure to see if the Panny is changing all intensity levels or just the one sampled - or are you just agreeing it easier to see the changes at the brighter levels? The Sanyo changes it for all intensity levels - but only for a narrow hue range around the sampled color.

FWIW

This is what HomeTheater mag gets for the Sharp 12KmkII

Red Color Point: x=0.655, y=0.333 Green Color Point: x=0.325, y=0.633 Blue Color Point: x=0.147, y=0.054

http://www.hometheatermag.com/images/archivesart/306sharp.6.jpg

The text points out the green is tinged yellow compared to the mkI - so make sure you are comparing to the proper version in the reviews to see if you are tracking. But theirs is not as far yellow green as some of you. FGMs before looks closest to this.

FWIW

This is what HomeTheater mag gets for the Sharp 12KmkII

Red Color Point: x=0.655, y=0.333 Green Color Point: x=0.325, y=0.633 Blue Color Point: x=0.147, y=0.054
The text points out the green is tinged yellow compared to the mkI - so make sure you are comparing to the proper version in the reviews to see if you are tracking. But theirs is not as far yellow green as some of you. FGMs before looks closest to this.Yes, but this is what they got BEFORE applying the CMS. In fact, HTM seems blissfully unaware that the Sharp projectors even have a CMS.

FGM and Bob Sorel's 12Ks have even worse greens AFTER using the CMS.

anbjornk

Did you measure to see if the Panny is changing all intensity levels or just the one sampled - or are you just agreeing it easier to see the changes at the brighter levels? The Sanyo changes it for all intensity levels - but only for a narrow hue range around the sampled color.

I just agreed with you :) I do not know what the AE1000 system do exactly. but I know it's not good enough. Are there testpatterns I can use to check these things?

It can, and yes.

I don't know that you need help. It sounds like you are doing just fine. Meters often start to lose accuracy below 30 IRE, especially if you are taking readings off the screen, so I wouldn't worry about that too much. See your PM.

Reason I'm asking is that if I use your methodology I may nail the 30%/90% combination (or similarly 30%/80%) with 0.313,0.329 but still find that the middle ranges (40%-70%) are showing 0.310, 0.321 or similarly. I figure that I need to alter the Blue cuts/gains to "lift" these up. I'm taking measurements pointing at the lens (emissive) at about 5 feet.

As you can tell, I'm "missing" some education here on the mechanical aspects of how the controls alter the grayscale. I think I'm trying to make the grayscale alignment be as smooth and close to D65 as possible (lowest dE) throughout the range. I have found that I run out of blue at the top-end of the Ruby. Guess that's the nature of the Xenon lamp.

What I've found, with my particular projector, is that to bring the "middle" in line with the suggested IRE points, I need to:

a)really reduce Blue bias while increasing R/G bias, and
b) reducing Red gains while doing some slight adjustments to G/B gains.

Any help in understanding these mechanisms would be appreciated. What's interesting is that the Ruby is trickier to work with than the Sanyo Z5 I've also calibrated.

Here is a comparison of the two methods for adjusting color/tint on my Benq PB6200 FP. First, I adjusted the color and tint using the blue filters and Getgray(see file: blue filter method.jpg). Next, I used the 75% method described at the beginning of this thread (see file: 75% method.jpg).

As you can see, there is quite a difference between results of each method. I am not sure which one to go with. The blue filter method result has smaller delta E values so I would guess that I should go with that one. However, with what I have read on this forum, the 75% method is more accurate. Would it be better to just adjust the tint in the blue filter method to bring cyan closer to the target? The third image (compromise.jpg) is a color and tint both set to default (0). Maybe I should just adjust the tint (bring cyan up to the target) on those settings - let me know what you think. - Thanks.

Here is what Home Theater Mag measured:

Here is a comparison of the two methods for adjusting color/tint on my Benq PB6200 FP. First, I adjusted the color and tint using the blue filters and Getgray(see file: blue filter method.jpg). Next, I used the 75% method described at the beginning of this thread (see file: 75% method.jpg).

As you can see, there is quite a difference between results of each method. I am not sure which one to go with. The blue filter method result has smaller delta E values so I would guess that I should go with that one. However, with what I have read on this forum, the 75% method is more accurate. Would it be better to just adjust the tint in the blue filter method to bring cyan closer to the target? The third image (compromise.jpg) is a color and tint both set to default (0). Maybe I should just adjust the tint (bring cyan up to the target) on those settings - let me know what you think. - Thanks.This display obviously has a severe color decoding error, so severe that to set red Y correctly you must seriously undersaturate red in xy. I'd just leave Color at 0 and set tint according to the Cyan coordinate as described.

It may not be the decoder, I think he is using a magenta filter on the output.

The blue filter method result has smaller delta E values so I would guess that I should go with that one. However, with what I have read on this forum, the 75% method is more accurate.
dE is your measure of accuracy, but but do know what flavor of dE you are using (they are not all equal). If you are having to make tradeoffs between having the correct quantity of light vs. the correct quality of light, then that can be a hard choice as Tom indicates.

Bill

angryht

aligning the secondaries by coordinate may not work as well if you have not first done the greyscale. It is obvious when your cyan and magenta are too blue/purple and your whites are too blue/purple that this is a greyscale issue - not a tint issue.

This is indicated by the alignment that you got with the filters - it is "correct" for that incorrect greyscale - the secondary lines are nearly crossing at the white point. The cyan will not be on target even if you have aligned with filters simply because the white point is not on the D65 target.

Now if you have aligned the greyscale best you can - then trying to hit the secondary coordinates per the specs rather than alignment with filters or incorrect white points - is a reasonable compromise - if you can. But you will never accomplish that without color/tint per CMY - as the global tint can only rotate around the incorrect white point you will only get one secondary correct.

And even if you do get the white point at D65 - the secondary lines will not perfectly cross because the red/green primaries are off.

It may not be the decoder, I think he is using a magenta filter on the output.

I am not using any filters on the output. I am taking readings off of the screen.

angryht

aligning the secondaries by coordinate may not work as well if you have not first done the greyscale. It is obvious when your cyan and magenta are too blue/purple and your whites are too blue/purple that this is a greyscale issue - not a tint issue.

This is indicated by the alignment that you got with the filters - it is "correct" for that incorrect greyscale - the secondary lines are nearly crossing at the white point. The cyan will not be on target even if you have aligned with filters simply because the white point is not on the D65 target.

Now if you have aligned the greyscale best you can - then trying to hit the secondary coordinates per the specs rather than alignment with filters or incorrect white points - is a reasonable compromise - if you can. But you will never accomplish that without color/tint per CMY - as the global tint can only rotate around the incorrect white point you will only get one secondary correct.

And even if you do get the white point at D65 - the secondary lines will not perfectly cross because the red/green primaries are off.

Attached is the grayscale achieved prior to doing any adjustment of the color and tint in the user menu. When I was done with the adjustments I did a quick check of the grayscale using the 10 points and it was consistent with the values prior to the adjustments. In other words I think my grayscale is pretty good.

This display obviously has a severe color decoding error, so severe that to set red Y correctly you must seriously undersaturate red in xy. I'd just leave Color at 0 and set tint according to the Cyan coordinate as described.

I think I will give this a shot.

Now if you have aligned the greyscale best you can - then trying to hit the secondary coordinates per the specs rather than alignment with filters or incorrect white points - is a reasonable compromise - if you can. But you will never accomplish that without color/tint per CMY - as the global tint can only rotate around the incorrect white point you will only get one secondary correct.

Maybe one or two clicks to split the difference?

Thanks again for the responses.

aligning the secondaries by coordinate may not work as well if you have not first done the greyscale. It is obvious when your cyan and magenta are too blue/purple and your whites are too blue/purple that this is a greyscale issue - not a tint issue.

This is indicated by the alignment that you got with the filters - it is "correct" for that incorrect greyscale - the secondary lines are nearly crossing at the white point. The cyan will not be on target even if you have aligned with filters simply because the white point is not on the D65 target.

Now if you have aligned the greyscale best you can - then trying to hit the secondary coordinates per the specs rather than alignment with filters or incorrect white points - is a reasonable compromise - if you can. But you will never accomplish that without color/tint per CMY - as the global tint can only rotate around the incorrect white point you will only get one secondary correct.

And even if you do get the white point at D65 - the secondary lines will not perfectly cross because the red/green primaries are off.
Agreed. A slightly different take on Tom's procedure that may work on some people's units:

1) Adjust the Red, Green and Blue Primaries in the CMS. The secondaries should move as the primaries are adjusted, but don't worry about their accuracy just yet.

2) Calibrate the grayscale. As Kraz mentions, the secondaries will move around as the balance between the primaries is adjusted to hit white.

3) Adjust the location of the secondaries in the CMS. The secondaries ought to be fairly spot-on with most "normal" color systems after #2, but some may not be. This will especially be true if there is a dedicated "scondary primary", like the DLP color wheels that have Yellow filters in them (I'm not sure of any CMS-enabled displays that have odd color wheels, but I'm sure they are coming; this is true for using an external box with color controls, though).

4) Adjust the color decoder (color/tint). This ought to be changed internally as the CMS is adjusted, but it may not be.

You may want to swap #3 and #4 in my procedure above, depending upon how your display is designed/responds. Also, always re-check the grayscale after #3 and #4. A well-designed unit should not have the grayscale altered by changing secondaries, but reality trumps theory so you have to check.

Bill

If your grayscale was correct - then you have one of those displays with the color decoder assuming a 9300K greyscale - something that has happened before (an Optoma that had one scan rate but not the others do this). If that is the case then try adjusting the 9300K preset to be D65 if you can.

I personally find incorrect yellows most offensive so that is the compromise I would lean to.

If your grayscale was correct - then you have one of those displays with the color decoder assuming a 9300K greyscale - something that has happened before (an Optoma that had one scan rate but not the others do this). If that is the case then try adjusting the 9300K preset to be D65 if you can.

I personally find incorrect yellows most offensive so that is the compromise I would lean to.

Krasmuzik: I think you found the issue!!! Brilliant!!! I am pretty sure have a color temperature that is set to 9300K, at least that is what I think, based on the service manual and some independant testing. The color temperature in the user menu has values from -50 to +50. It appears that the -50 is the default for 6500K, the 0 is for 9300K and the +50 is for the 11500K. When I did the gray scale adjustment before, I had set the projector to 0 to adjust grayscale not knowing that the color decoder may be assuming a color temp based on the user menu setting.


I will set the color temp to -50, adjust grayscale and then try the color/tint adjustments.

I'll let you know how it turns out.

Thanks again, I really appreciate your thoughts.

I spent several hours re-calibrating my Epson TW700 projector with this method. I have some questions:

The Epson Tw700 projector only allows you to finely adjust using either RGB adjustments (grayscale) OR RGBCMY adjustments (colourspace) and not both at the same time. (i.e. when adjusting grayscale using RGB, the TW700 locks you into a predefined colourspace that within the CIE is accurate for red, blue and yellow, but off for green, cyan and magenta. Furthermore, this predefined colourspace when red is 21% of white, only shows blue as 4% of white and green as 95% of white).

Thus, which is better:
To have a well calibrated colourspace and poorer grayscale? (using other adjustments in the menu for setting better grayscale while adjusting colourspace, I can't get dE below 4 from 40-100 and below 10 for 0-40)?

Or is it better to have a well calibrated grayscale (dE below 3 for 20-100) but having an inaccurate colourspace?

Sorry for the convoluted question, but I really must know. Overall I think grayscale hits more accuracy points between grayscale and colourspace.

I spent several hours re-calibrating my Epson TW700 projector with this method. I have some questions:

The Epson Tw700 projector only allows you to finely adjust using either RGB adjustments (grayscale) OR RGBCMY adjustments (colourspace) and not both at the same time. (i.e. when adjusting grayscale using RGB, the TW700 locks you into a predefined colourspace that within the CIE is accurate for red, blue and yellow, but off for green, cyan and magenta. Furthermore, this predefined colourspace when red is 21% of white, only shows blue as 4% of white and green as 95% of white).

Thus, which is better:
To have a well calibrated colourspace and poorer grayscale? (using other adjustments in the menu for setting better grayscale while adjusting colourspace, I can't get dE below 4 from 40-100 and below 10 for 0-40)?

Or is it better to have a well calibrated grayscale (dE below 3 for 20-100) but having an inaccurate colourspace?

Sorry for the convoluted question, but I really must know. Overall I think grayscale hits more accuracy points between grayscale and colourspace.
This question isn't convoluted at all. Welcome to the real world of calibration where the limitations imposed on you by the available controls on the display limit what you can accomplish.

From your description, this display has some fairly serious color decoding errors, which you cannot adjust at all. Beyond that, the only choice is custom grayscale or accurate color points, but not both.

There probably is no RIGHT answer, but rather a judgment you have to make based on your own viewing preferences. One thing I would like to know is in what way the gray scale is off at 40IRE and below. Is it excess blue? If so, that would be more tolerable than excess red or green.

If I were you, I would seriously consider an external processor, if it's in your budget. The Optoma HD3000 would allow you to get a nearly perfect gray scale and fix the color decoding errors. Of course, it costs as much as a new projector. Unfortunately, without spending more money, there is no ideal choice.

It is blue that is off the most. Red and Green actually track pretty close together to ideal. Blue is 8-15% off in general.
Here are my dE values by IRE:
20=17
30=12
40=11
50=8
60=7
70=7
80=6
90=6
100=3
Overall, the colour temperature histogram shows of course a cooler temp.

The above calibration was accomplished by setting Colour temp to 6000K, and adjusting a setting called Skin Tone on my projector, whereas the RGB calibration with proper grayscale tracking allowed me to use a Colour temp value of 6500K.

I'm just used to have a dE below 3 across the board when using the RGB controls.
Just to clarify, when grayscale is calibrated with RGB, and thus tracks very well, the CIE chart in turn shows Red, Blue, and Yellow are right on the reference points for 709. Green is the most off (lying above the reference), and cyan and magenta are slightly off.
BUT, when I try to make red, green and blue balance as percentages of white (as per your calibration tips), that's where I see them the most off from the 21%, 70% and 8% they should be at (as previously mentioned).

How can the CIE look pretty good for blue, but be so off on the percentages when adjusting colour overall?

This question isn't convoluted at all. Welcome to the real world of calibration where the limitations imposed on you by the available controls on the display limit what you can accomplish.

From your description, this display has some fairly serious color decoding errors, which you cannot adjust at all. Beyond that, the only choice is custom grayscale or accurate color points, but not both.

There probably is no RIGHT answer, but rather a judgment you have to make based on your own viewing preferences. One thing I would like to know is in what way the gray scale is off at 40IRE and below. Is it excess blue? If so, that would be more tolerable than excess red or green.

If I were you, I would seriously consider an external processor, if it's in your budget. The Optoma HD3000 would allow you to get a nearly perfect gray scale and fix the color decoding errors. Of course, it costs as much as a new projector. Unfortunately, without spending more money, there is no ideal choice.

Spent several hours last night calibrating TB1 mode for both my HTPC (DVI/HDMI cable feeding 720p) and my Xbox 360 (component cable feeding 720p, but 480p for the GetGray as I don't have HD test patterns and that's how the 360 works).
Also worth mentioning is I use a 106" Carada BW screen, and the projector is 15' away.

I used the Pantone Eye-One LT probe with HCFR software & GetGray patterns. I used the 709 colour reference setting as most of what I watch is HD material, but this does cause a problem (see section "What's left to do").

I used the RGBCMY calibration, rather than the RGB calibration. I had previously been running with a calibrated RGB only for both components, but as mentioned in the Cine4Home review, the colours were oversaturated, so I decided to go further with the RGBCMY calibration.

Calibration Method:
1. Gamma: Multiple Grayscale readings to adjust gamma curve (achieved Gamma of 2.26 for HTPC & 2.23 for 360).
2. Overall Colour: Read 75% white window and adjusted overall colour setting until Red showed as 21% of the white reading.
3. Grayscale: Adjusted Colour Temp and Skin Tone settings while doing continuous readings and looking at grayscale until dE was the lowest from 40-100 IRE.
4. Colourspace: Adjusted each RGBCMY Hue and Saturation setting while taking continuous readings and looking at the CIE chart. Dial-in each colour to the best reference triangle areas. This is tricky, for as each colour was dialed in I also looked at the continuous data readings and readjusted Saturation onthe currently calibrated colour so that I achieved the best compromise for each colour's % of reference white at 75%, which is the following:
Red = 21% of reference white
Green = 70% of reference white
Blue = 8% of reference white
It's important to note that I never compromised a good placement on the CIE chart for more accurate colour balance on the data readings, since for green these two were in conflict.
5. Final adjustments: Performed a complete grayscale, primary, and secondary set of measurements and made minor adjustments where needed.

Results:
The result is a colour space pretty much dead on D65 and a grayscale with a dE of about 4 from 40-100 IRE, so I'm ecstatic about the results. I'll post my chc files later to this post.
However, I really do have to get used to D65. The colours are severely unsaturated compared to what I have been watching up until now.
The other thing I now notice much more with the properly calibrated projector is a substantial increase of noise/grain in the picture. This must be a result of the largely reduced saturation in colours (my colour is at -5, with most individual RGBCMY colour saturations averaging about -90). Any explanation here would be appreciated.

Projector Settings:
I'll post my complete settings later by editing the post, but here is what I can remember off the top of my head:

HTPC:
White Level = 13
Black Level = -5
Colour = -5
Tint = 0
Colour Temp = 5500K
Skin Tone = 3
DVI Level = Expanded

Xbox 360:
White Level = -4
Black Level = -3
Colour = -5
Tint = 0
Colour Temp = 6000K
Skin Tone = 3
Setup Level = 0%

Eye-One vs Spyder2Express:
The Eye-One is more accurate through the IRE, and especially in the 20-40 range.
For me it's well worth the extra expense, mainly because I'm obsessed with properly calibrated display devices
It also takes much faster readings than the Spyder for the 40-100 IRE range, and slightly slower for the 0 to 40 IREs when you choose "Average many readings for dark" setting in HCFR.

Whats left to do:
1. Enjoy the beautiful picture of course, but also I need to find some good settings from these 2 component calibrations for my Sonicview 8000HD FTA receiver, which of course I cannot play test patterns on. Best I can do is record the HDNET patterns and adjust white, black and colour and tint.
2. Rec 709 vs 609: On the 360, the GetGray patterns are displayed on in 480p rather than 720p, as the 360 sends it this way. Since I don't have HD patterns like DVE HD (just came out), I cannot calibrate properly for 709, even though that's the setting I used in HCFR even though the 360 outputs the patterns in 480p. I think I will create two settings, one calibrated at 709 and 609 to see if it matters for HDDVD material. Any advice on this would be appreciated.

BUT, when I try to make red, green and blue balance as percentages of white (as per your calibration tips), that's where I see them the most off from the 21%, 70% and 8% they should be at (as previously mentioned).

How can the CIE look pretty good for blue, but be so off on the percentages when adjusting colour overall?Because these are 2 totally different measurements of color performance that are more or less independent, as I pointed out in the original guide.

- Gray scale
- Color Decoding
- Color Gamut

are independently adjusted. One can be good and the others not good. You have control over gray scale OR Gamut, but not both simultaneously. You have no control over the color decoder other than the user Color/Tint controls. This is not uncommon. Most displays have no way to adjust color decoding. Other than setting color/tint, ignore this and focus on gray scale and/or gamut irregularities.

Because these are 2 totally different measurements of color performance that are more or less independent, as I pointed out in the original guide.

- Gray scale
- Color Decoding
- Color Gamut

are independently adjusted. One can be good and the others not good. You have control over gray scale OR Gamut, but not both simultaneously. You have no control over the color decoder other than the user Color/Tint controls. This is not uncommon. Most displays have no way to adjust color decoding. Other than setting color/tint, ignore this and focus on gray scale and/or gamut irregularities.

Thanks. That helps a lot.

I have tried to calibrate the Optoma HD7100 pj which has the following adjustments:
-In the user menu: contrast, brightness, sharpness, colour, tint, gamma, color temperature in 500 steps plus x,y adjustment, and RGBYCM gains and offsets.
-In the SM: Color wheel adjustment, lightness, colour and tint for RGBYCM, VGA auto calibration, MST 9888 component YPbPr, AD 9888 VGA RGB and SAA 7118.
Since I am using the DVI input, colour, tint, VGA autocal, MST 98088, AD 9888 and SAA 7118 are grayed out and NOT available. Therefore, I have used the RGBYCM lightness, colour and tint adjustments instead of overall colour and tint to do the calibration described by Tom in this thread.
Attached is the “before” file, done with a DTP-94 colorimeter reading off a white eggshell screen placed about 2-3 feet from the lens surface. The DTP-94 was just above the pj’s lens looking towards the screen. Doing the reading in this way I have improved the low end range/accuracy substantially as compared to reading from the screen proper at 10 ft from the projector. The patterns are those of the HCFR dvd disc which is in PAL and the pj plays it in PAL if in auto mode. Is this OK for calibration purposes? Should I have the projector to output a NTSC signal from the PAL dvd input signal? Or should I have the dvd player to output a NTSC signal to the projector?

Although the signal from the Bravo D1 dvd player has been upscaled to 720p I am using the rec. 601 colour space for the measurements by HCFR because I am unsure as to what the dvd player and the pj actually do with that signal; any comments on this? Is there a way to know if the dvd player/pj are using rec 601 vs. rec 709?

I have used the DVI input, set the gamma at 2.2, colour temperature at 6500K and sharpness to softest setting. All other settings are default.
I first tried to adjust the gamut as best as possible, then I tried to adjust the lightness value of the RGBYCM as a percentage of white lightness. Then I refined the intersection at the D65 point by slightly adjusting the Y tint and M tint and then run and adjust the gray scale until it looks OK. I had to do a couple of small adjustments to the gamut and the D65 point position which had been affected by the gains and offsets adjustments for gray scale. Then I had to re-adjust again the lightness values as percentage of white lightness until they are all within +/- 2% of the respective theoretical value. Attached is the “after” file.
I feel that I could improve a bit the dE of B in the gamut and improve the gray tracking from 20-80 IRE with a little tweaking of the gains and offsets.
However, I have not touched the contrast and brightness. From past experience, I know that to achieve the blackest blacks and the whitest whites I could use something like B=-13 and C=+9 but this will make a bell shaped gamma log curve and add colour to the grays at 80 IRE or so.
Any comments/observations welcome.
I would also like to report that when adjusting the lightness of the primary colours, I was expecting HCFR to report an equivalent change to the adjacent secondary colour lightness but that did not happened. It is like the concept of the lightness of say yellow = Glightness+Rlightness did not apply. In other words, if I increased the value of green lightness the values of yellow and cyan were not affected (or very little affected).
Can anybody explain??
Thanks for looking.
Fermin

What is the Y value of reference white?

What is the Y value of reference white?

Brightness?

Brightness?I'm not asking for a definition. I'm asking for a number.

I'm not asking for a definition. I'm asking for a number.


Oh, sorry. Mine is about 11.2

What is the Y value of reference white?

I take it is the Y of the 100 IRE Gray.
"Start" file Y=1108.55
"After" file Y=873.84

Well, OK, but 873.84 is not the number in the HCFR file you provided. It lists 920.67. However using the new number as a reference, your display shows some rather profound color decoding errors in red and blue.
R +11.4%
G -4.0%
B + 28.8%
This assumes a SMPTE-C color space.

You can't get it any better than this using the Value adjustment?

Well, OK, but 873.84 is not the number in the HCFR file you provided. It lists 920.67. However using the new number as a reference, your display shows some rather profound color decoding errors in red and blue.
R +11.4%
G -4.0%
B + 28.8%
This assumes a SMPTE-C color space.

You can't get it any better than this using the Value adjustment?

Tom,
Thank you for the comments. The errors you have observed are probably due to my having attached the wrong "after" file to my original post. I have already corrected the mistake (edited the post).
I apologize for the confusion this mistake may have caused.

OK, using the updated file, then the calibrated Optoma HD7100's color is very, very accurate, among the best available. FYI, I get an average dE of 4.68.

To get some idea of how good this is, a current very popular and much more expensive projector measures an average dE of over 30.

Tom,
Thanks, this is great news.
What do I do now with contrast, brightness and gamma? If I try to max the dynamic range by decreasing the brightness to the best possible black level and then after I adjust contrast per S&V calibration dvd, the gamma curve will be negatively impacted and one or more colours will most likely get clipping badly and/or the high IRE gray levels will take a colour shade.
Is there a way to adjust contrast by using colorimeter measures and HCFR and thereby preventing clipping and/or colored grays?
What should I go for: a nice ,flat gamma or the best possible dynamic range w/o clipping and coloured grays? I do not think I can have both.
All comments/opinions welcome.
Thanks.
Fermin

There is only one correct setting for black level. Use a pluge pattern and lower brightness until the 2 IRE bar disappears. Then raise it just enough so that the 2 IRE bar is visible again but the below black information remains invisible.

Contrast is a little trickier. In principle you adjust contrast in the same way. Raise the Contrast until a 98 IRE bar disappears against a 100 IRE background. Then lower it just enough so that the 98 IRE bar is visible again. There are 2 differences with this procedure and setting black level.

1. It is not critical that the above white information disappears. Many displays will continue to show above white when contrast is set properly.

2. The procedure described above often leads to a contrast setting that is too high because the display cannot maintain color accuracy at the high end just below clipping. In such cases, lower the contrast further until you can maintain a reasonably accurate gray scale out to 100 IRE.

2. The procedure described above often leads to a contrast setting that is too high because the display cannot maintain color accuracy at the high end just below clipping. In such cases, lower the contrast further until you can maintain a reasonably accurate gray scale out to 100 IRE.

A question about this advice:
Is it necessary to find the exact point that you can raise contrast while not affecting colours at 100 IRE? I mean, could contrast be set slightly lower than that point and still provide maximum contrast for the display?

Tom,

On the GetGray DVD there are step patterns (0 to 256?? digital) for each of the primary colors (RGB). I have noticed that when I set contrast as usually directed (2 IRE just visible, or equivalent), the upper steps of one or more RGB patterns are crushed. Is this of significance? Should contrast be lowered to remove the crush or is there some other adjustment that is needed.

Also, I have read about determining the "limiting color" and then when adjusting the grayscale to not increase the gain of the "limiting color." Could you comment on the concept of "limiting color," its significance, and how to determine it.

Thanks much for taking on this thread.

I mean, could contrast be set slightly lower than that point and still provide maximum contrast for the display?Why would you want to set it LOWER than the point where you have achieved color accuracy? For what reason? You've already set it lower than clipping would recommend. Setting even lower just wastes available dynamic range.

Also, I have read about determining the "limiting color" and then when adjusting the grayscale to not increase the gain of the "limiting color." Could you comment on the concept of "limiting color," its significance, and how to determine it.This is exactly what I referred to above. Many displays will not give an accurate gray just below clipping because one or more of the colors doesn't have enough dynamic range (it's usually red). Then you have to lower the contrast until you can achieve a reasonably neutral gray at 100 IRE.

Hey guys,

A short but sweet update. My new 12k has much better uniformity, so far no flicker (only 5 hours though), and better OOTB color accuracy. The Spyder2 and the DTP-94 are very close in performance as long as you keep the light levels up for the Spyder (by placing it closer to, and facing the pj). I'm assuming the DTP is more accurate, but in this configuration, the Spyder is much faster. So, I'll use the Spyder to get a preliminary calibration, then fine tune it with the DTP.

On another subject, I beleive it was Tom that mentioned that my RGB levels (especially Green) were lower than should be necessary for a proper calibration on this unit. The reason they were so low was my method, posted on the forum quite awhile back, by Guy Quo. His method was basically, center Brightness/Contrast, set Red and Blue Offset too low and use Green Offset to set Brightness (make BTB match backround). Return Red and Blue Offsets to default. Then, set Red Gain to highest that doesn't cause clipping. Then use only the Green and Blue Gains, and the Red and Blue Offsets to calibrate. I've always assumed this was correct. I mean Guys knows what he's talking about...right?

Rob

robbyc30

That is they way I have always done things. Some calibrators prefer to calibrate at 80% rather than 100% though - and are willing to put up with the color shift on hot whites for the better contrast numbers. I get annoyed when highlites shift or clip - so I do it Guy Kuo's way. Also it leaves user brightness/contrast for source variation adjustment without having to worry about greyscale interactions.

Of course you want to generalize it and find out what these clip limits are - it is not always red on gain and green on offsets.

Why would you want to set it LOWER than the point where you have achieved color accuracy? For what reason? You've already set it lower than clipping would recommend. Setting even lower just wastes available dynamic range.

Thank you, you've answered my question.

Of course you want to generalize it and find out what these clip limits are - it is not always red on gain and green on offsets.Krasmuzik... Just out of curiosity, how would one determine what are the clip limits?

If your sensor software has a RGB% histogram then whenever it stops changing when you increase the RGB gain - it is clipped. Or you can use RGB ramp test patterns and try to sense the clipping by eye same as you would for the contrast white levels. If 90% white is on D65 target but 100% white is too cyan - it is likely clipped on Red.

HD-DVE has RGB (10IRE) step patterns which can help diagnose gross clipping as well.

Mark

I and many others have made the assumption that if the display decodes in Rec709, even if the the original source was Rec601 transcoded to Rec709 by a dvdplayer, that we should calibrate primaries to Rec709. Now I think that may be incorrect, consider the two cases:

1. RGB->YCbCr(601) (at telecine) : MPEG2->YCbCr(601) (480i/p at dvdplayer)-> : YCbCr(601)->RGB (at display)

2. RGB->YCbCr(601) (at telecine) : MPEG2->YCbCr(601)->Transcode->YCbCr(709) (720p/1080i at dvdplayer) : YCbCr(709)->RGB(at display)

We all can agree that case 1. should yield Rec601 primaries. In case 2. the transcode step is necessary for a display which assumes the Rec709 colorspace whenever an HD transport stream is used but the end result, the RGB vector should be identical to the one in case 1, shouldn't it? Otherwise we will have changed the intent of the original color vector. In other words, the 1st encoding step defines what Red Green and Blue are and subsequent decode/encode steps are not allowed to change that original definition. Thoughts, counter arguments? I am now thoroughly confused on this.

The DVD player has to do the transcode properly - rather than stretching REC601 out to REC709 - it needs to limit RGB to within the REC601 gamut within the REC709 gamut - which means limiting the YCbCr signal. An SD picture in a HD signal should appear to be a desaturated HD signal - and not made 'extra super vivid bonus' picture. Now which option do you think marketers choose that they 'think' customers prefer - especially if it cost no engineering resources to do?

The DVD player has to do the transcode properly - rather than stretching REC601 out to REC709 - it needs to limit RGB to within the REC601 gamut within the REC709 gamut - which means limiting the YCbCr signal. An SD picture in a HD signal should appear to be a desaturated HD signal - and not made 'extra super vivid bonus' picture.

This sounds like you agree that for color accuracy when we use SD source patterns, even those that go through the transcode step, we should tweak the display to reproduce SD primaries? Is that correct?

No - the signal is in REC709 so you should use REC709 primaries - however the signal itself is going to be desaturated so it never exceeds SMPTE-C gamut. Even if they choose to do it right (unlikely) - very likely they will not give you the control over the transcode process.

Since it is likely that REC709 sources itself was mastered on a SMPTE-C monitor - there are those who say don't even using REC709 primaries to begin with. If you do that - then the upconverted DVD problem solves itself if transcoding done wrong - but get even more desaturated if they did it right. These cross format codec and display isssues makes it near impossible to guarantee you see what the mastering engineer saw.

No - the signal is in REC709 so you should use REC709 primaries - however the signal itself is going to be desaturated so it never exceeds SMPTE-C gamut. Even if they choose to do it right (unlikely) - very likely they will not give you the control over the transcode process.


I think that just restates my original post. If it's done right and you will never see colors outside the original SMPTE-C gamut then as a calibration issue you can only use this test pattern to align to the original SMPTE-C gamut. If it's done wrong, by stretching one gamut to the other, then it that case I agree you should align to Rec709.


Since it is likely that REC709 sources itself was mastered on a SMPTE-C monitor - there are those who say don't even using REC709 primaries to begin with. If you do that - then the upconverted DVD problem solves itself if transcoding done wrong - but get even more desaturated if they did it right. These cross format codec and display isssues makes it near impossible to guarantee you see what the mastering engineer saw.

This was another issue that I was going to throw into the OP but glad you brought it up. Does there exist an equivalent to a SMPTE-C monitor for Rec709? If HD is being mastered with a calibration to SMPTE-C phosphors, then regardless of the encoding matrices we should be calibrating everything to SD primaries.

We are both right - I was thinking using RGB to align the gamut to aviod issues - you are using upconverted YCbCr to align the gamut.

Guy Kuo was insistent that nobody uses HD gamuts in mastering only SMPTE-C. He no longer posts here - maybe he will if they ever do start mastering HD with HD gamuts. Hopefully you have enough calibration memory to go both ways!

So does this mean that when playing an upconverted DVD (let's say through a HTPC) than the display should be on a mode that is calibrated to 601; while when playing HD material than the display should be on a mode that is calibrated to 709?

Or shoudl the upconverted DVD be played on modes calibrated to 709 as well?

......
Guy Kuo was insistent that nobody uses HD gamuts in mastering only SMPTE-C. ........!
This post by Glimmie (http://www.avsforum.com/avs-vb/showthread.php?p=9818147#post9818147) indicates to me that for movies made from the digital intermediate process, home video is now coming from an underlying CIE XYZ colorspace..

CIE XYZ colorspace is founded on human perception limits - so I am not sure what Glimmie is claiming it does alien-only colors - rather it would be correct to say it can store colors that currently cannot be displayed unless we have multi-primary laser systems. The new support for outside gamut colors in HDMI1.3 could take advantage of full CIE XYZ if we ever get a media format founded on Digital Cinema - neither high def DVD format supports this - so you can forget home movies in this format - maybe PS3 will do video games this way though. But you still need something to display it on.

All that RGB is is an abstraction that later assigns the RGB primaries to an XYZ color- the true measure of color seen by humans - so an XYZ colorspace is not limited by intended primaries but its RGB based display most certainly is..

The color space of DigitalCinema is irrelevant - the question is what monitor are they color correcting it on? Is it the same as the Digital Cinema Projector - or is it a SMPTE-C monitor? Home video formats are founded on D65 - film and Digital Cinema are founded on different white points - this means home video has to be color corrected for its own format. Which means somebody will look at it it and sign off on it looking right - unless they want to rely on transcoders getting it right via 'perfect' math - and the directors don't want the opportunity to make artistic compromises to fit the larger gamut into a smaller one.

So does this mean that when playing an upconverted DVD (let's say through a HTPC) than the display should be on a mode that is calibrated to 601; while when playing HD material than the display should be on a mode that is calibrated to 709?

Or shoudl the upconverted DVD be played on modes calibrated to 709 as well?


Under the assumption that when dvd players upconvert they map 601 primaries to 709 primaries then for calibration purposes you can use a 601 encoded gamut to calibrate your display for 709 material. i.e. if the transcode process is simply this:

YCbCr(601)->RGB->YCbCr(709) with no tinkering of the RGB values.

However, 601(or more properly SMPTE-C) mastered disks encoded in rec601 when upconverted with this transcode process will display colors not intended by the colorist. Of course you can avoid this whole issue by playing the disk in 480i/p and let your display do the upconvert. Your specific question though is "should I set the display to use rec601 primaries with upconverted SD material", and I think the answer to that is yes, again assuming the player truly maps one color space to the other. If after the transcode process all we do is this:

YCbCr(709)->RGB, the RGB values chosen during the mastering process are preserved.

Think of it this way, at the beginning of the chain is a SMPTE-C phosphor, if all the encode/decode steps are color neutral(meaning the RGB values are not mucked with) at the end of the chain (your display) you want SMPTE-C phosphors.


As far as HD material goes it's not clear what the correct color space to use is and somebody more familiar with HD mastering please chime in. But my thinking is that if the colorists are really using SMPTE-C reference then it depends on whether the encoding process is fudged to preserve this color within the wider rec709 gamut (in which case you would set your display to rec709) or whether, like the dvd player example, the primaries are mapped directly to rec709 in which case rec601 primaries at the display would be appropriate.

Hi, gang.

I've been reading up on the Plasma pages over the last couple of months and have finally settled on the Panasonic TH-58PZ750U. It's scheduled to be delivered this week, but I'm trying to line up everything I'll need beforehand...including calibration specifics.

I'll have to admit that the content of this thread is somewhat foreign to me, but I'm coming up to speed on devices, DVDs, and terms fairly quickly.

The question I have is fairly simple: What changes to calibration are needed, given this new "Studio Reference Mode" feature that is available on the new 750Us?

According to Panaconic, the Studio Reference Mode "enables the replication of colors that was originally intended by the director—exactly the way they are seen on reference monitors in professional film editing rooms."

The manual for the 750U (http://service.us.panasonic.com/OPERMANPDF/TH50PZ750U.PDF) (careful...it's 30M) has more specifics on pages 32/33, and 56. Here are the Picture menu and sub-menu options (pgs. 32/33):

• Normal
• Picture mode
• Picture, Brightness, Color, Tint, Sharpness
• Color temp.
• Color mgmt.
• C.A.T.S.
• Pro setting
• Zoom adjust
• PC adjust
• Other adjust
• Video NR
• 3D Y/C filter
• Color matrix
• Block NR
• Mosquito NR
• Black level
• 3:2 pulldown
• HD Size


Here is the text from page 56 Technical Information, regarding the "Pro Setting":

•Normal: Resets all Pro setting adjustments to factory default settings. (Set/No)
•Panel brightness: Selects the display panel brightness.
(High: Vivid, Mid: Standard, Low: Studio ref)
•Contour emphasis: Adjusts the contour emphasis of the image. (On/Off)
•Gamma adjust: Gamma correction. Adjusts the intermediate brightness of the image. (Normal/Mid/Full 1/Full 2)
•Black extension: Adjusts the dark shades of the image in gradation.
•W/B high R: Adjusts the white balance for light red areas.
•W/B high B: Adjusts the white balance for light blue areas.
•W/B low R: Adjusts the white balance for dark red areas.
•W/B low B: Adjusts the white balance for dark blue areas.
•AGC: Increases the brightness of dark signal automatically. (On/Off)


Is this new "Mode" just a marketing term for switching some Service Menu features to User Menu OR is this feature a realistic way of gaining a truer representation of colors for the end user? How does this mode change the calibration steps...if at all?

Thanks in advance!


P.S. Sorry for the lenthy post, but I'm sure many others have or will have the same question.

Based on the previous posts, I think it would be safe to think/state that when a dvd player does the upconversion AND outputs the signal through DVI(RGB) then it does not matter whether it has done the upconversion in the 601 or 709 space since , logically, when converting the signal back to RGB(DVI) it will use the same coding it used to upconvert it and will output in all cases the original /intended RGB signal. Right??
In the affirmative, wouldn't the display that gets an RGB signal tthroughDVI at its native resolution just display that RGB signal received in the same way, wwhetherit is SD or HD; yes??
In the affirmative, then, when using DVI, the primaries should be calibrated to rec 601.
When using a component connection, the problem remains whole: has the dvd player done the transformation to rec 709? since the display will receive a YCbCr signal that it will have to convert and has no way to know what colour space was used by the dvd player.
Kras, zoyd: does this make any sense?
Thanks ,
Fermin.

FGM

You cannot make blanket assumptions. What primaries does the display use with an RGB input - REC709 (same as sRGB)? Or does it use uncorrected native primaries? Or does it send RGB through a video codec to add back in video controls - and now it is REC601 and SMPTE-C?

Here are the Picture menu and sub-menu options (pgs. 32/33):

• Normal
• Picture mode
• Picture, Brightness, Color, Tint, Sharpness
• Color temp.
• Color mgmt.
• C.A.T.S.
• Pro setting
• Zoom adjust
• PC adjust
• Other adjust
• Video NR
• 3D Y/C filter
• Color matrix
• Block NR
• Mosquito NR
• Black level
• 3:2 pulldown
• HD Size


Here is the text from page 56 Technical Information, regarding the "Pro Setting":

•Normal: Resets all Pro setting adjustments to factory default settings. (Set/No)
•Panel brightness: Selects the display panel brightness.
(High: Vivid, Mid: Standard, Low: Studio ref)
•Contour emphasis: Adjusts the contour emphasis of the image. (On/Off)
•Gamma adjust: Gamma correction. Adjusts the intermediate brightness of the image. (Normal/Mid/Full 1/Full 2)
•Black extension: Adjusts the dark shades of the image in gradation.
•W/B high R: Adjusts the white balance for light red areas.
•W/B high B: Adjusts the white balance for light blue areas.
•W/B low R: Adjusts the white balance for dark red areas.
•W/B low B: Adjusts the white balance for dark blue areas.
•AGC: Increases the brightness of dark signal automatically. (On/Off)


Is this new "Mode" just a marketing term for switching some Service Menu features to User Menu OR is this feature a realistic way of gaining a truer representation of colors for the end user? How does this mode change the calibration steps...if at all?Most of this is useless and should be turned off. The W/B High/Low adjustments are for tuning the gray scale. You need equipment for this. Other than that, the promise of this Pro mode is that the color points will be more accurate than what the Pannys typically offer, which is very oversaturated greens.

That's it. Now you should go back and remeasure gray scale, color decoding, and saturation/tint because there may have been interaction between these adjustments. You may have to go through two or three rounds of taking these measurements until all are correct.

One quick question about remeasuring color decoding. I have been doing all of the adjustment using the 75% color windows, but when I am done adjusting, I measure using the 100% color windows and look at the CIE diagram. Is that right or should I be using the 75% windows for the final measures?

The reason I ask is because of this quote in the getgray calibration dvd documentation:

"Some devices color-decoders work well at 75% levels but are inaccurate at other levels."

One quick question about remeasuring color decoding. I have been doing all of the adjustment using the 75% color windows, but when I am done adjusting, I measure using the 100% color windows and look at the CIE diagram. Is that right or should I be using the 75% windows for the final measures?The whole point of the color decoding measurement is getting a correct proportion between white and RGB. To get this they ALL have to be at the same level. Also, the CIE chart has nothing to do with color decoding.

In this faq (http://www.accupel.com/Calibration_FAQ_f.html) written by Greg Rogers he has an optimization procedure for color accuracy when dealing with non-standard primaries which involves moving the white point:

"To optimize the color accuracy of a display that does not have the correct primaries you can use the following procedure. First draw a color gamut triangle using the measured primary color values as the vertices of the triangle. Then pick a proposed new color temperature near the D65 standard. Draw a line from each primary color through the proposed new color temperature and extend it until it intersects the primary triangle. The complementary colors should lie at the intersections with the color gamut triangle. Select the best new color temperature that simultaneously minimizes the color accuracy errors of the three complementary colors. Measure the complementary colors to verify the results."

I typically try to minimize the error in the secondaries with reference to the standards whereas this technique minimizes errors with reference to the gamut your primaries actually create. From a color science point of view, what is the advantage of this technique where all the saturation lines intersect at the (non-D65) white point but the deltaE with reference to the standard can be quite high?

FGM

You cannot make blanket assumptions. What primaries does the display use with an RGB input - REC709 (same as sRGB)? Or does it use uncorrected native primaries? Or does it send RGB through a video codec to add back in video controls - and now it is REC601 and SMPTE-C?


OK, fair comment. I am just testing thoughts/ideas in relation to calibrating a source/display/screen in an industry that appears to be quite anarchic in its implementations. I have no idea of what primaries the pj uses with an RGB input. What should "normally" be expected?
I am using an upsampling SD dvd player (Bravo D1) that may or may not apply rec 709 when outputting YCbCr 720p and 1080i signals. I am even more confused as to the primaries it uses when it outputs an RGB 720p or 1080i signal through DVI. Then, I have an HD capable dlp pj (Optoma HD7100) that I assume applies rec 601 to SD signals and rec 709 to HD signals. Thanks God, the screen is passive although it has a gray tint to it and it is retroreflective (Optoma Graywolf II).
For calibration I have the Optix Monaco colorimeter, HCFR, S&V and THX calibrating dvds and HCFR software.
If you were called to professionally calibrate this chain when using a DVI 720p at 48Hz and "native" mode with no scaling done by the projector, what factors do you know apply to the chain, what would you do and what assumptions would you be making? Would you calibrate it to rec 601. 709, other? Would you try to bring RGBYCM to the CIE? Would you want to get RGBYCM values right as a percentage of the white Y value? What would you rather have, a flat gamma log line or maximize the dynamic range yet preserve as pure whites as possible?
When using DVI, the pj offers a CMS with RGBYCM lightness, saturation and tint, adjustable gamma values by 500k, adjustable colour temperature by 500K with x,y adjustment, RGBYCM gains and offsets, sharpness, contrast and brightness.
Kras, zoyd, Tom, others, please??

In this faq (http://www.accupel.com/Calibration_FAQ_f.html) written by Greg Rogers he has an optimization procedure for color accuracy when dealing with non-standard primaries which involves moving the white point:



I read this as pick a non D65 white point that gets your secondaries closer to the REC709 target - since secondaries are just the primaries subtracted from white. This agrees with what I have said before - primaries you are often stuck with while you are white adaptable - but natural colors are mostly within the secondary gamut - so get it right first.

Look at the gamut backwards - start at the REC709 secondaries - draw a line over to measured primaries - where they nearly intersect is your compromise white point.

Look at the gamut backwards - start at the REC709 secondaries - draw a line over to measured primaries - where they nearly intersect is your compromise white point.

After rereading the procedure I agree, picking an optimum white point will move the secondaries closer to spec and reduce error.

Attached are my latest. I reduce color to get luminance (Y) to 21% for red and 9% for blue (Rec 601). Green stayed around 51%. When I adjust tint the yellow and cyan move towards green. I adjusted it as close to the targets for both. Is there any way to move magenta closer to the target? I am also curious if I should try to adjust my color temp based on Greg Rogers' method or the variations discussed here.

Any help would be appreciated.

Here is my grayscale.

After rereading the procedure I agree, picking an optimum white point will move the secondaries closer to spec and reduce error.

That's a very interesting idea. But color pictures also have black and white and gray. As long as our gray scale is at least in the ballpark, that might be a very good compormise.

BTW, the Hitachi DIrector Series (and similar higher end models) plasma displays have full color management and be tuned up to be super performers.

Chuck

angryht

Indeed looks like making your white point a bit yellow (less blue or more red/green) might get the secondaries on track. You will find that only small error in white leads to a greater shift in secondaries perceptual error.

angryht

Indeed looks like making your white point a bit yellow (less blue or more red/green) might get the secondaries on track. You will find that only small error in white leads to a greater shift in secondaries perceptual error.

Thanks, Kras. Any thoughts as to what color temp would get a better result. Here's what I am thinking: if I project a line from my measured green to the target magenta it intersects the black body curve at about 6000K. So if I change the color temp to closer to 6000K, my magenta should get closer to the target, right? I guess I am a little uneasy about changing from the 6500K. Is this a common thing to do with DLP projectors, inherently undersaturated green values?

Thanks, Kras. Any thoughts as to what color temp would get a better result. Here's what I am thinking: if I project a line from my measured green to the target magenta it intersects the black body curve at about 6000K. So if I change the color temp to closer to 6000K, my magenta should get closer to the target, right? I guess I am a little uneasy about changing from the 6500K. Is this a common thing to do with DLP projectors, inherently undersaturated green values?
Don't think about this in terms of changing color temperature from 6500K to 6000K, and forget about the blackbody curve. There are lots of CIE x,y values that would produce a correlated color temperature of 6000K. You want to find the best x,y point to minimize the complementary color errors and use that x,y point. Draw lines (3) from the primaries through a potential x,y point and pick the x,y point that minimizes the errors at the complementary colors (where the lines intersect the primary color triangle. If you don't move too far from D65 you probably won't notice the difference in grayscale color temperature, compared to the improvement in the overall color accuracy. (Advanced tip: It is actually better to do this using the u',v' color space if you have a way of making those measurements.)

Don't think about this in terms of changing color temperature from 6500K to 6000K, and forget about the blackbody curve. There are lots of CIE x,y values that would produce a correlated color temperature of 6000K. You want to find the best x,y point to minimize the complementary color errors and use that x,y point. Draw lines (3) from the primaries through a potential x,y point and pick the x,y point that minimizes the errors at the complementary colors (where the lines intersect the primary color triangle. If you don't move too far from D65 you probably won't notice the difference in grayscale color temperature, compared to the improvement in the overall color accuracy. (Advanced tip: It is actually better to do this using the u',v' color space if you have a way of making those measurements.)

OK. Now I think I am getting it now. Here is the file in u'v' mode. Why is it better to do it in u'v' color space?

Don't think about this in terms of changing color temperature from 6500K to 6000K, and forget about the blackbody curve. There are lots of CIE x,y values that would produce a correlated color temperature of 6000K. You want to find the best x,y point to minimize the complementary color errors and use that x,y point. Draw lines (3) from the primaries through a potential x,y point and pick the x,y point that minimizes the errors at the complementary colors (where the lines intersect the primary color triangle. If you don't move too far from D65 you probably won't notice the difference in grayscale color temperature, compared to the improvement in the overall color accuracy. (Advanced tip: It is actually better to do this using the u',v' color space if you have a way of making those measurements.)

Doesn't this assume that the secondary is always aligned through the white point to the primary? If you look at angryht's CIE diagram the line connecting blue to yellow does not pass through his current white point.

Doesn't this assume that the secondary is always aligned through the white point to the primary? If you look at angryht's CIE diagram the line connecting blue to yellow does not pass through his current white point.

But when I adjust the tint, cyan and yellow move. So I was going to start with magenta and then adjust tint. Does that make sense?

Make sure your tint is aligned first - greyscale is irrelevant for aligning tint when you use the blue filter method - because you have 'bluescale'. Since your color decoder appears to be hardset to 9300K white point - this means your magenta/cyan will be too blue - you then fix that by moving towards yellowish whites (color temp is irrelevant)

u'v' is better because it focuses more on magenta - the eye sees more of those hues than green. The u'v' chart shows a small error in white will lead to a larger error in magenta.

Is it possible the imperfection in secondary axis crossing is just sensor slightly off on primary readings?

Save a preset with off secondaries yet a perfect D65 result vs. perfect secondaries and whatever white that gets. Flip back and forth I think you will see the trick works quite well - in fact you will notice every time you switch that the white you switched to is wrong and the old one was right - because you adapted to it! No matter the direction of the switch! But the colors being off - you don't adapt.

Make sure your tint is aligned first - greyscale is irrelevant for aligning tint when you use the blue filter method

So, should I use tint to adjust the cyan and yellow so it is lined up with the target values then adjust the gray scale so it lines the magenta up?

It seems that everytime I adjust the grayscale the magenta is always lined up with the colortemp of white. And since my green is shifted towards red so much, the line between green and magenta always puts magenta towards blue.

u'v' is better because it focuses more on magenta - the eye sees more of those hues than green. The u'v' chart shows a small error in white will lead to a larger error in magenta.

Is there a simple way (equation) to convert my xyY data to u'v'. I am using HCFR and there is no option for that.

BTW, the Hitachi DIrector Series (and similar higher end models) plasma displays have full color management and be tuned up to be super performers.Chuck

I have a Directory Series RPLCD, and although it has hue and gain for primaries and secondaries, it doesn't seem to have anything for saturation. Is there something in the service menu?
Roy

angryht

See my spreadsheet at the end of the sticky charts thread...

So, should I use tint to adjust the cyan and yellow so it is lined up with the target values then adjust the gray scale so it lines the magenta up?


NO - I am saying adjust the tint first they same way you would without the sensor - using AVIA and your blue filters. to get cyan/magenta balanced with blue optically filtered.

Then do the measurements and adjust greyscale for best secondaries.

It seems that everytime I adjust the grayscale the magenta is always lined up with the colortemp of white. And since my green is shifted towards red so much, the line between green and magenta always puts magenta towards blue.

which is why you need to make your white more red - it makes magenta more red. But you actually want to make white more yellow so that there is more green in cyan as well.

White point shifted blue-red axis shifts mostly Magenta - White point shifted blue-green axis shifts mostly Cyan - White point shifted red-green axis shifts mostly Yellow. They key is finding the interactive balance so Magenta, Cyan,Yellow hit their target.

angryht

See my spreadsheet at the end of the sticky charts thread...

Got it. Thanks.

NO - I am saying adjust the tint first they same way you would without the sensor - using AVIA and your blue filters. to get cyan/magenta balanced with blue optically filtered.

Then do the measurements and adjust greyscale for best secondaries.


Thanks you for the clarification. I will do that then adjust the grayscale based on the comments you provided above.

Once again thanks.

I have a Directory Series RPLCD, and although it has hue and gain for primaries and secondaries, it doesn't seem to have anything for saturation. Is there something in the service menu?
Roy

Roy, I was referring to Hitachi's Director Series plasma displays, which have saturation, hue, and intensity settings for primary and secondary colors, as well as color decoder alignments. By aligning the color decoder first (and, as I recall, it's very close already), then applying the full CMS, you can get an outstanding picture from these Hitachi plasmas.

Chuck

Actually, I need to amend my last statement.

I just looked over my notes to be sure, and it looks like I may be somewhat mistaken. Yeah, it seems to be an actual, true CMS, but no level controls for the colors. It allows gain and phase controls for primary and secondary colors, plus a color decoder alignment that allows levels for red and green only, so that can possibly get you in the ballpark. I worked on this about three months ago, so I didn't have the benefit of Tom Huffman's color decoding spreadsheet. But it really looked wonderful, once it was tweaked, and had a more than acceptable black level.

Chuck

Picking up on the SMPTE-C vs 709 primaries discussion a little ways back, I took some measurements of the HDnet test patterns here (http://www.avsforum.com/avs-vb/showthread.php?p=10862976&&#post10862976). It appears that the color bars are mastered for SMPTE-C primaries and encoded in such a way that they will be reproduced correctly using 709 primaries at the display end.

which is why you need to make your white more red - it makes magenta more red. But you actually want to make white more yellow so that there is more green in cyan as well.

White point shifted blue-red axis shifts mostly Magenta - White point shifted blue-green axis shifts mostly Cyan - White point shifted red-green axis shifts mostly Yellow. They key is finding the interactive balance so Magenta, Cyan,Yellow hit their target.

Well, I think I've got it much closer now. Attached are my before and after CIE plots. I adjusted the white point toward yellow by increasing the red and green gains. That got magenta right in line with the target. Then I adjusted tint slightly and the yellow and cyan fell right into place. Then I verified that the grayscale tracked consistently throughout the percent stimulus. Looks pretty good.

So here is what I did:
1. Adjusted my 'user menu' color control until I was as close as I could get to the the 75% white as described in the first post of this thread. Actually, the best I could do was to get red and blue close to the target 21% and 9% (SMPTE-C). My green is only about 50%, which I would guess is fairly common for DLP projectors that are trying to be bright more than they are trying to project acurate colors.
2. Set my 'user menu' tint per getgray and the blue filter.
3. Adjust white point slightly towards red and yellow to get magenta towards the target. I used the constant measures in HCFR.
4. Double check that the grayscale tracks consistently throughout the percent stimulus.
5. Check contrast and brightness one more time then call it a day.

I must say that skin tones look much more natural.

Looks like you got it - I think as you watch it more you will realize the secondary gamut is most important.

on the Hitachi vs810 LCD RPTV, the user menu has color decoding, and color management sub menus.

controls in the color decoding menu

Red
Green
Color
Tint

controls in the Color Management menu

Magenta -> Phase & Gain
Red -> Phase & Gain
Yellow -> Phase & Gain
Green -> Phase & Gain
Cyan -> Phase & Gain
Blue -> Phase & Gain

following the instructions here for color and tint will not involve the Red and Green controls in the decoding menu. The Color control has more effect on the Blue than Red or Green. Once all the primaries and secondaries are as close to the CIE chart as possible, skin tones have a clay hue to them.

Should I use the color decoding menu controls to set blue Y to 8% of white, red Y to 21%, and green Y to 71%, then follow through to the color management? or ignore the decoding menu and just use the color management settings?

thanks
vega

You are making the common mistake of using the color controls to sacrifice color brightness (the decoding) significantly enough that it impacts color saturation (the gamut). You have to measure xyY when you adjust - not just xy. It does not appear you have any color saturation control - you cannot shrink/enlarge your gamut properly.

The color decoding menu is for your video - the color management is for your display. You can isolate the display by avoiding the color decoder if you have a reference RGB source, unless yours is one of those that runs RGB thru the video codec.

Should I use the color decoding menu controls to set blue Y to 8% of white, red Y to 21%, and green Y to 71%, then follow through to the color management? or ignore the decoding menu and just use the color management settings?Yes. Use the standard color control to set blue and then use Red and Green to set each of those levels.

Regarding color management, I guess Phase means Tint, but I'm not sure what Gain means. It usually refers to a gray scale adjustment, but since it's in the color managment section it may mean something different here. What happens when you adjust one color's Gain control up/down?

thanks Tom and krasmuzik for your replies .......

Phase moves the color toward one of the other 2 adjacent colors. eg Phase for the blue, would allow adjustment toward cyan, or magenta. The gain controls, as far a sI can tell, adjust the intensity of the color. I'm not sure how this differs from the color decoding controls.

this set's CMS has a lot of adjustment. The green was way too high on the y axis out of the box, and I can bring it down, but the Y value seems to go well below where it should be. I believe that on this set the green cannot be reigned in without grossly under saturating it.

I read over the Calman instructions and remember seeing Bill mention that some digital sets have one primary over saturated, and there is not much to be done, other than to find a good compromise.

If I try to get the green to a compromise, which value (x, y, or Y) is the most important?

You should be using dE as your error measure rather than optimizing one thing over the other. dE gives the perceptual error in the xyY measures (if implemented properly).

Usually if you do not have proper controls you cannot fix out of gamut primaries - but turning down the color only a bit can make them appear less annoying.

The gain controls, as far as I can tell, adjust the intensity of the color. I'm not sure how this differs from the color decoding controls.Thats's just what I was wondering. If you adjust red gain, does the position of red change on the CIE chart or does the color just become more or less bright? If it's the latter, then it is just repeating the color decoding controls that are already there. Something of a disappointment.

Tom

adjusting the gain for any of the colors does move the position on the CIE chart. I tried using the decoding menu as follows

set color Y (blue) to 8% of white Y
set red Y to 21%
set green to 71%
adjust tint to get cyan as close as possible to it's CIE location

then in the CMS I adjusted each color to get the lowest dE. The color has improved a great deal. All colors with the exception of green have a dE less than 2, green is 10.8, and shows well above the mark (y value high) on the CIE chart. I can move the green to the location on the CIE chart, but dE goes to 37.

I repeated the process 2 more times, and color improved each time. I did notice the adjustments were getting smaller with each calibration.

Which green setting would be closer to correct, the lowest dE as krasmuzik suggests, or the closest location on the CIE chart?

then in the CMS I adjusted each color to get the lowest dE. The color has improved a great deal. All colors with the exception of green have a dE less than 2, green is 10.8, and shows well above the mark (y value high) on the CIE chart. I can move the green to the location on the CIE chart, but dE goes to 37.

I repeated the process 2 more times, and color improved each time. I did notice the adjustments were getting smaller with each calibration.

Which green setting would be closer to correct, the lowest dE as krasmuzik suggests, or the closest location on the CIE chart?So you can't use the Gain control to affect saturation without its also affecting color brightness? If that's the case, then get the lowest dE possible. If green has a dE of 10.8, that's not bad. Some expensive digital projectors have a dE of 30 or more for the green primary.

dE increases because your Y value drops drastically when you moved the gain control to get it over to the right x,y. As noted earlier this gives watercolor video - you don't want to do this. Go with the lowest dE. Getting the hues corrected on primaries, and secondaries on target will make for a good picture once you have corrected the brightness decoding.

When I change the gain control in CMS, x,y, and Y all change. when the phase is adjusted, only x and y change. The green control in the color decoding changes Y the most, and seems to have a larger effect on Y than the CMS. Changing the color decoding values has a minor impact on grayscale, the CMS adjustments have less or no effect on grayscale (I'm guessing this is a good thing).

I have repeated the above steps three times, and have seen an improvement each time. I also see the adjustments are getting smaller each time. Blue Red and Magenta did not need any change on the last run.

When I change the gain control in CMS, x,y, and Y all change. when the phase is adjusted, only x and y change. The green control in the color decoding changes Y the most, and seems to have a larger effect on Y than the CMS.I wonder if you could use the Gain control to get the xy right and then use the Color Decoding control to raise the Y value back to where it should be while leaving the xy point mostly unchanged.

I'll try your suggestion, and post the results tomorrow.

thanks
vega

I wonder if you could use the Gain control to get the xy right and then use the Color Decoding control to raise the Y value back to where it should be while leaving the xy point mostly unchanged.

Well it's a mixed bag, the CMS and the color decoding adjustments both change x,y, and Y values, but in different ways. The Y value is predictable, move the control to the + and it increases. The x, and y values differ, in CMS y changes are more pronounced, in the color decoding, x changes are more pronounced (this is also changed with the phase control). I managed to get dE down to 8.1, at the expense of cyan and yellow increasing to @ 2.8. Anything lower and the green looks washed out. It may be my eyes, as I have had this set for over 2 years, and to this point only calibrated the grayscale.

I did notice the color control will affect all colors, but blue by far the most. Should I try to move the color control higher and correct the levels for all P&S in the CMS? OR would I be spinning my wheels here? How would I determine the best trade-off at this point?

thanks
vega

How would I determine the best trade-off at this point?You'll just have to experiment to see what gets the best results, though it's starting to look like the 10.8 for green is the best you are going to do.

Engineering a true saturation control seems to be a real technical hurdle. This is the one control whose presence indicates you have a fully functioning CMS.

Reason is Tint/Phase Color/Gain controls are simple math - adjusting the gain is a multiplication of a component - adjusting the phase multiplies two components . A CMS requires on the fly 3x3 matrix math - with a user interface that converts from perceptual adjustments back to matrix coefficients.

thanks for all the help, I've learned a lot, and have improved the color on my set while doing so. Looking at some of the other posts here, and other threads, I guess I'm lucky to get as close as I have.

vega

Hi,
I tried to calibrate my pio 5080 using HCFR and a spyderII with DVEHD. Not a good experience. Pretty much just getting garbage numbers for the primary and secondary color. negative x and ys. That sorta thing. Strangely enough with the filter off I can get what appears to be a very reasonable grayscale. Any thoughts???

Hi,
I tried to calibrate my pio 5080 using HCFR and a spyderII with DVEHD. Not a good experience. Pretty much just getting garbage numbers for the primary and secondary color. negative x and ys. That sorta thing. Strangely enough with the filter off I can get what appears to be a very reasonable grayscale. Any thoughts???I do. Don't use the Spyder2.

I do. Don't use the Spyder2.

Does the i1pro have stability problems when it starts to heat up? Any special problems using it for plasmas? I've read here that it is a pain to use. Some pro calibrator claimed in this forum that for most sets he'd just use the D2 even though he also had the I1pro.

Does the i1pro have stability problems when it starts to heat up? Any special problems using it for plasmas? I've read here that it is a pain to use. Some pro calibrator claimed in this forum that for most sets he'd just use the D2 even though he also had the I1pro.I haven't experienced any stability problems. It was probably me who you refer to about liking the D2 and how the i1Pro was something of a pain to use. All true, but I would still use it with plasmas. It just takes a little more patience with the repeated dark readings.

OK, I used Tom's method for setting the RGB to the designated percentages of white. Why do we change to using the x,y dE as the guide for CMY? What happens if you use the percentage of white for the CMY? Some of the dE's I was seeing were in the 150-300 range. Changing hues did not seem to affect the dE as much as it affected Y. I ended up setting CMY to the proper percentage in spite of the dE and the picture looks great. I don't get it.

VM

OK, I used Tom's method for setting the RGB to the designated percentages of white. Why do we change to using the x,y dE as the guide for CMY? What happens if you use the percentage of white for the CMY? Some of the dE's I was seeing were in the 150-300 range. Changing hues did not seem to affect the dE as much as it affected Y. I ended up setting CMY to the proper percentage in spite of the dE and the picture looks great. I don't get it.

First, there is no "change" when going to the secondaries. It is just that if the Y of the primaries is correct, the Y of the secondaries should be also. In my experience, there is just no need to adjust them independently. However, if it's required on your display, then by all means do so. That may or may not also be true of xy. This could vary from display to display.

Second, dE is determined by xy AND Y. How are you calculating dE? Changing hue will have an effect on xy, Y, and the dE, and from this you conclude. . . . what exactly?

I don't get it either.

First, there is no "change" when going to the secondaries. It is just that if the Y of the primaries is correct, the Y of the secondaries should be also. In my experience, there is just no need to adjust them independently. However, if it's required on your display, then by all means do so. That may or may not also be true of xy. This could vary from display to display.

Second, dE is determined by xy AND Y. How are you calculating dE? Changing hue will have an effect on xy, Y, and the dE, and from this you conclude. . . . what exactly?

I don't get it either.

I am using Sencore CP500 software to calculate dE. I guess my question is "How can the Y be on the mark with x,y so very far off?

I am using Sencore CP500 software to calculate dE. I guess my question is "How can the Y be on the mark with x,y so very far off?I covered this in my initial article. Y, or more commonly referred to as "color decoding" is a separate phenomenon from gray scale tracking and color gamut (xy points) and is adjusted independently via separate controls, though they do have interactive effects.

I don't know how the Sencore software calculates dE. Some calibration software (I think HCFR falls into this category) calculates dE solely on the basis of xy and ignores Y. CalMan, on the other hand, considers all xy and Y, although in a somewhat idiosyncratic way. I don't think ColorFacts even has a measure of dE for the primaries/secondaries. I believe that it reports dE for gray scale only.

Thank you, Tom. I'll check with Sencore.

OK, I did check with Sencore. They're reply is -

"True delta E does take into acount the full difference in the appearance of
two colors, including their luminance. This is usually calculated in a more
uniform color space than the CIE 1931 xy space.

For our purposes, we are concerned only with the chromaticity differences
between a reference white point, and the color of white achieved by a
particular display, so we ignore the luminance. We designate the metric as
dExy, which we calculate as sqrt((x1-x2)2 + (y1-y2)2). This tells us the
coordinate distance, on the xy plane, that the chromaticity of one color is
from another."

Tom, you didn't indicate the software package you use. What is it? Is there a work around for software with just a dExy?

OK, I did check with Sencore. They're reply is -

"True delta E does take into acount the full difference in the appearance of
two colors, including their luminance. This is usually calculated in a more
uniform color space than the CIE 1931 xy space.

Tom, you didn't indicate the software package you use. What is it? Is there a work around for software with just a dExy?

You can use the spreadsheet provided by Krasmuzik found here (http://www.avsforum.com/avs-vb/showthread.php?p=10265204&&#post10265204) , which will calculate deltaE in the more perceptually uniform CIELUV colorspace and includes the effect of errors in luma. Currently the colorHCFR package calculates deltaE using only chromiticity error which is fine for grayscale calibration as sencore states. The next version of this software includes the CIELUV based deltaE.

Tom, you didn't indicate the software package you use. What is it? Is there a work around for software with just a dExy?I use lots of different stuff: Colorfacts, CalMan, and HCFR. It all depends on what I'm doing.

Probably the best workaround is a Zoyd suggests. Manually enter the xyY data into Kraz's spreadsheet and it will get you what you are looking for. HCFR will work well for this as well when they get around to releasing V. 2.

Hello gang, I have read here and on other topics that the CMS on the Pioneer elite's don't work. I would have believed that before but not now. I have calibrated my 1130 using the CMS controls and get what I consider a very good picture. But it only seems to work well in one of the many different picture modes. not sure why. Anyway my question for Tom is I have done the 75% white/red method for setting color. Tint is a little different because of the CMS it moves. Not a problem because you can move it back. Why can't you use a software program to set the secondary colors? Could you use equal parts of red and blue to get magenta, and equal parts of blue and green to get cyan? Or is it not a question of equal parts of the two colors but there location on the CIE chart. When I get a moment I will include my grayscale for the Pioneer. :confused:

OK anyway here is my files. :D

I don't think ColorFacts even has a measure of dE for the primaries/secondaries. I believe that it reports dE for gray scale only.


It has a raw data window which provides many colorspace coordinates- the dE it reports is w.r.t. to white. So you can read a color and get a dE - but unless you know the dE for the target color w.r.t. to white and can do vector math - a bit meaningless. A Proper dE would use the desired color target, a proper calibration tool would also give you chart instruments you can see from across the room. The reality is almost all calibration software on the market is designed for grayscale tuning - not color decoding and gamut tuning - pretty sad state of affairs considering grayscale has become a minor part of calibration work for decent digital displays - it is the color decoding and gamut displays intentionally are screwing up!

Hello gang, I have read here and on other topics that the CMS on the Pioneer elite's don't work. I would have believed that before but not now. I have calibrated my 1130 using the CMS controls and get what I consider a very good picture. But it only seems to work well in one of the many different picture modes. not sure why. Anyway my question for Tom is I have done the 75% white/red method for setting color. Tint is a little different because of the CMS it moves. Not a problem because you can move it back. Why can't you use a software program to set the secondary colors? Could you use equal parts of red and blue to get magenta, and equal parts of blue and green to get cyan? Or is it not a question of equal parts of the two colors but there location on the CIE chart. When I get a moment I will include my grayscale for the Pioneer. :confused:I am baffled by this one. I spent several hours on the 1130. I could get the CMS to move the color points, but doing so screwed up the grayscale. I couldn't get them both right at the same time. What mode did it work in and what occurred in the modes where it didn't work?

Yes, some sets have color decoding adjustments that allow you to adjust the hues of the secondaries--Sony CRTs for example. The tint control adjusts the amount of blue and green in cyan. That's why changing the tint control moves cyan towards either of its associated primaries.

I am baffled by this one. I spent several hours on the 1130. I could get the CMS to move the color points, but doing so screwed up the grayscale. I couldn't get them both right at the same time. What mode did it work in and what occurred in the modes where it didn't work?

Yes, some sets have color decoding adjustments that allow you to adjust the hues of the secondaries--Sony CRTs for example. The tint control adjusts the amount of blue and green in cyan. That's why changing the tint control moves cyan towards either of its associated primaries.

Tom it is possible that your instrument is too inaccurate to do CMS such that it will not wreck gray scale for that display. When you skew CMS too far it can really make a mess. The following is some data for my EyeOne Pro versus my narrow band PR-670 for 10 displays of the same model. The variance is even more problematic when you start looking a different models. I believe a good CMS requires a very high end instrument to avoid problems.

Tom it is possible that your instrument is too inaccurate to do CMS such that it will not wreck gray scale for that display. When you skew CMS too far it can really make a mess. The following is some data for my EyeOne Pro versus my narrow band PR-670 for 10 displays of the same model. The variance is even more problematic when you start looking a different models. I believe a good CMS requires a very high end instrument to avoid problems.No, it had nothing to do with the instrument. The problem was NOT subtle. This user also saw the same problem with all of the picture modes except one. It never occurred to me to make the adjustments in a different picture mode.

Just got through calibrating the Sharp 12K following Tom's instructions. I had to reduce contrast to eliminate red clipping using a 100IRE 75% window. I also chose a gamma I wanted and got that in the ballpark before I started on grey scale and color. I used a 6K temp setting--6500 setting on Sharp proved to actually be 7K. I got better results just dialing down temp from the outset, rather than pulling it down with just gain and offset controls. My final result was almost identical to Tom's results shown here http://www.avsforum.com/avs-vb/showthread.php?t=862447 Big surprise was that Color setting went from +1 to +14 when I used the red as a % of white method. Overall, color improvement after calibration is dramatic.

My only remaining issue is RGB gamma tracking. My RGB gamma tracks pretty tightly until 80-90IRE. In log mode, at 90IRE, with an average gamma of 2.5, R goes up to 2.6 and B down to 2.35. Is there a rough guide to how much divergence you can have before it is noticeable in the picture?

Big surprise was that Color setting went from +1 to +14 when I used the red as a % of white method. Overall, color improvement after calibration is dramatic.You should use the RGBCYM Value control in the CMS to adjust for decoding, rather than the Color control, which affects all colors equally.

Is there a rough guide to how much divergence you can have before it is noticeable in the picture?None that I know of.

You should use the RGBCYM Value control in the CMS to adjust for decoding, rather than the Color control, which affects all colors equally.

None that I know of.


Thanks. I did use the CMS controls to adjust Green and Blue, but my interpretation of your instructions was that you use the Color control to adjust Red. Is the procedure for Red different because of the Sharp's CMS controls?

Edit: I mean I used the CMS to adjust GBCYM, and color to adjust R

Thanks. I did use the CMS controls to adjust Green and Blue, but my interpretation of your instructions was that you use the Color control to adjust Red. Is the procedure for Red different because of the Sharp's CMS controls?

Edit: I mean I used the CMS to adjust GBCYM, and color to adjust RExactly. The Sharp has precise controls for all of the colors, so you shouldn't use the Color control at all. Use Red Value to adjust the level of red. It's the same with Tint. Leave that alone. Use the Cyan Hue control instead.

The Sharp has more controls than most displays. You should be able to dial in nearly perfect color, except green which is shifted towards yellow (at least on the Mk II) to a degree you probably can't fully adjust out.

Thanks Tom, that makes perfect sense. I'll recheck it. I remember now that when I was setting the decoder for the other colors that I checked red too, and it was at 21% of white, so I may have ended up in the right place anyway, but I need to double check that.

Yeah, green is definitely the big outlier, cyan to much lesser extent. Every other color dials in perfectly.

Tom,

I redid my color calibration using only the lightness, chroma, and hue settings in the CMS (though I did leave saturation and tint at +1 for DVI, by oversight) . Of course, for the color decoder adjustments, the only control that mattered was lightness (value). I got the following values: White Y 18.59, Red target 3.9, G 13.2, B 1.49, C 14.64, M 5.3 and Yellow 17.26. I was able to achieve all but Red, which I could only get up to 3.09. This resulted in CMS settings below:


CMS Light Chroma Hue
R +24 , -8 , +4
G +18 , -21 , +1
B +22 , 0 , +12
C +19 , 0, +1
M +28 , -10 , +13
Y +22 , -23 , -3

I was surprised that the lightness adjustments had to be so large for each color. I did a similar adjustment for component input with color and tint set to 0 and got similar results. Are these in line with the CMS settings you ended up with?

I don't have the 12K. I have the 20K and its color decoder is spot on requiring virtually no adjustment. I can't speak to proper 12K settings, though I am surprised that you are getting these readings. What instrument are you using?

I don't have the 12K. I have the 20K and its color decoder is spot on requiring virtually no adjustment. I can't speak to proper 12K settings, though I am surprised that you are getting these readings. What instrument are you using?

A DTP-94. Maybe someone else who owns and has calibrated the 12K can tell me if my values suggest a bad colorimeter or projector. I PMed Bob Sorel to ask what he got. I could post HCFR file, but everything looks great (except green and cyan, of course) as far as grayscale, CIE, temp, gamma. All settings are as follows:

Post Calibration Settings for Sharp XV-Z12000 Mark II
High contrast iris position, economy bulb setting, Da-Lite HP screen

HDMI to DVI from Toshiba XA2 HD DVD Average Gamma 2.37

Contrast –5
Bright +1
Color +1
Tint+1
Sharpness 0
Temp 6000
Gamma C1
CMS 1


R Gamma -3
G Gamma 0
B Gamma +1

R Gain +2
G Gain –22
B Gain 0

R Offset +10
G Offset –1
B Offset –7

CMS Light Chroma Hue
R +24 -8 +4
G +18 -21 +1
B +22 0 +12
C +19 0 +1
M +28 -10 +13
Y +22 -23 -3

Component from Sony B-301 Blu-Ray Average Gamma 2.27 (don’t ask)

Contrast 0
Bright 1
Color 0
Tint 0
Sharpness 0
Temp 6000
Gamma C2
CMS 2

R Gamma -1
G Gamma -1
B Gamma -1

R Gain +3
G Gain -27
B Gain -5

R Offset 0
G Offset +1
B Offset -1

CMS Light Chroma Hue
R +21 -8 +5
G +19 -22 0
B +18 +5 +12
C +20 0 +3
M +26 -11 +11
Y +23 -23 +2

I calibrated my 12k with HCFR and a DTP-94. The color decoder was basically perfect, requiring no adjustments to the "Lightness" settings.

Rob

Thanks Rob,

I am thinking these are the possibilities: 1. DTP-94 needs adjustment or replacement 2. My projector's color decoder is defective 3. I somehow misread Tom's instructions and have incorrectly measured color decoder settings. My lightness settings do seem extreme. I have a Da-Lite HP screen and I am using high contrast mode and low bulb setting, but none of that would affect color decoder, as far as I know. I am using HCFR software and taking Y (luminance) reading from continuous measurments window. Then I calculate % of white (100% stimulation) targets from Tom's table of REC709 values and adjust Y using lightness for each individual color in CMS until I get as close as possible to target. It seems pretty straightforward. I could try averaging a large number of readings for each color to reduce measurment error, but I doubt that is the problem.

Jack

Are you sure your color patterns are at the same stimulus level as the white pattern?

Are you sure your color patterns are at the same stimulus level as the white pattern?

Thanks, I hadn't thought of that, but I am using GetGray. I assume that they are the same stimulus level, and I am using 75% windows for all measurements.

Jack

Post your HCFR file. Maybe we can figure it out from that.

Rob

Thanks Rob. Here are the HCFR files. I had to cut back on contrast substantially to eliminate a large clipping of red. On DVI, but not component, I have a whiter than white (WTW) showing 3 bars above 235 on a grayscale ramp (same for primary colors). I wonder if that has something to do with my odd color decoder settings. I have been discounting that as a factor because I am not getting WTW with component, and I need similarly large lightness increases in CMS to get its color decoder settings to match standards.

I have the DVI signal set to D video RGB. I will try computer RGB to see what happens.

Jack

Hey guys great thread, thanks Tom.

Take a look at my file and tell me what you think. This is with Toms method and only adjusting color and tint in the user settings. This is a Panny 900u with a DTP 94. I can get a perfect chart if I use the panny's CCM function but from what I understand about how it works there is no point in doing it. Correct me if I am wrong. Are these readings good enough as is?

75 white Y=7.67

R Y=1.62
G Y=5.69
B Y=3.40

Regarding color decoding performance, red and green are fine, but blue is much too low. Gray scale and gamma are good, but the chromaticity of red, yellow, and green are considerably off.

Hey guys great thread, thanks Tom.

Take a look at my file and tell me what you think. This is with Toms method and only adjusting color and tint in the user settings. This is a Panny 900u with a DTP 94. I can get a perfect chart if I use the panny's CCM function but from what I understand about how it works there is no point in doing it. Correct me if I am wrong. Are these readings good enough as is?

75 white Y=7.67

R Y=1.62
G Y=5.69
B Y=3.40

Based on your numbers, the 75% white window would be 10.32. If you measured RGB windows also at 75%, this gives

R: 27.4%
G: 110.8%
B: 12.5%

These numbers are way off. Only red is in the ballpark. What's up?

Thanks Rob. Here are the HCFR files. I had to cut back on contrast substantially to eliminate a large clipping of red. On DVI, but not component, I have a whiter than white (WTW) showing 3 bars above 235 on a grayscale ramp (same for primary colors). I wonder if that has something to do with my odd color decoder settings. I have been discounting that as a factor because I am not getting WTW with component, and I need similarly large lightness increases in CMS to get its color decoder settings to match standards.

I have the DVI signal set to D video RGB. I will try computer RGB to see what happens.

Jack

Based on your numbers, the 75% white window would be 10.32. If you measured RGB windows also at 75%, this gives

R: 27.4%
G: 110.8%
B: 12.5%

These numbers are way off. Only red is in the ballpark. What's up?

You hit the nail on the head. Zoyd zeroed in on it right away. I was too much of a blockhead to pick up on it. I used the 100% gray pattern and compared it to 75% amplitude color patterns! Why? Because I thought 75% pattern for color referred to size of the window. Stupid, huh? Even a cursory reading of the GetGray manual would have disabused me of that notion. Sorry for wasting your time.

Jack

Edit: BTW, I realized my error about a half hour before you posted your question--that's why my response seemed so quick. I was getting ready to write Zoyd to confess, when I saw your post.

Regarding color decoding performance, red and green are fine, but blue is much too low. Gray scale and gamma are good, but the chromaticity of red, yellow, and green are considerably off.

I could nail the CIE right on if I use the CCM function but from what I understand it only affects the selected color. Is it worth doing? or should leave it? How does the chromaticity being off on red, green and yellow affect the picture quality?

Here it is with the CCM applied.

Since all color is derived from combinations of red, green, and blue, if red and green are significantly off it will have a profound effect.

Regarding the CCM, what do your eyes tell you?

I could nail the CIE right on if I use the CCM function but from what I understand it only affects the selected color. Is it worth doing? or should leave it? How does the chromaticity being off on red, green and yellow affect the picture quality?

Since all color is derived from combinations of red, green, and blue, if red and green are significantly off it will have a profound effect.

Regarding the CCM, what do your eyes tell you?

Well on some scenes when I switch it on or off I can't see any change at all, but on others I can. Scenes with really bright colors are where it can be noticed the most especially in red areas and animated stuff. So I guess I will leave it on. Thanks for the input:)

What is interesting is that on the original adjustments before applying the color management settings, if I switch to rec 709 color space it lines up better. I wonder if that is telling me that my Denon dvd player is using rec 709 color space?

What is interesting is that on the original adjustments before applying the color management settings, if I switch to rec 709 color space it lines up better. I wonder if that is telling me that my Denon dvd player is using rec 709 color space?

That is the conclusion I would draw.

Yes, the Samsung LED DLPs have a CMS in the service menu, but it is not easy to use. Selecting the Movie preset gets you close.

Hello.

I am entirely new to the project of calibrating one's display, but I have what is, for me, an important question in this matter. Does anyone know if the new LED locally-backlit Samsung xx81F LCD tvs have proper Color Management Systems in them? I read Tom's very informative guide on page one and easily see the importance of having a well-functioning CMS. I just don't know if these rather quirky new Samsung displays have them.

Also, as I will be using a 4081F almost exclusively as an all-purpose/HTPC computer monitor, and as I have individual color controls in my ATI (X800) control panel, is it possible for me to circumvent color management limitations in the display via that control panel? I assume there are at least some potential down-sides to such a move, yes?? What would they be?

Any help or advice is greatly appreciated, especially since I have not yet purchased any calibration equipment at all, but am ready to go with a Display2 colorimeter, GetGray, and HCFR, if indeed the color controls in my display and/or graphics card support the sort of fine-tuning these tools offer.

Yours,

David Schenk

Hi all,

Is there any preference as to whether one should select a device to output HDMI RGB as opposed to component HDMI YCbCr (providing the device supports both - see PS3, oppo 970hd etc), when calibrating a system?

If so what is the compromise (if any) with some source devices which only output HDMI YCbCr (ie a Sat Reciever, tosh HDDVD hd-e1 (or ax1 in US I think) etc)

My thinking is since most of the digital displays will output anything (over HDMI) as HDMI RGB, it is better to have the source outputting HDMI RGB too (?) avoiding any color space issues that come from sources mis-matching SD ITU 601 to HD ITU 701 when using HDMI component (thinking of upscaling/upconverting players here). But is it the case?

Many thanks,

Kostas

This is not what we mean by a Color Management System. The NTSC specification requires ALL displays to have adjustments for Color, Tint, Sharpness, Brightness, and Contrast. A CMS goes significantly beyond this.
I really liked your instructions, they arevery clear, I only have some terminology problems. I own a Sony HS60 and it has Color, Hue, Brightness, Contrast and Sharpness, also individual RGB Gain/Bias.

There is no tint? How does this effect your instructions?

There is no tint? How does this effect your instructions?
hue = tint

hue = tint
Thank you. I got confused because in the first post both terms are used, why?

Steps from the first post:
Setting Color/Tint
Adjust the gray scale
Adjusting the Color Decoder
Adjusting Hue and Saturation

Saturation = color or is it?

Tom,

Is it possible to answer my question in post 213? It'd really help clarifying things (at least for me but I am sure for others as well).

Many thanks,

Kostas

If your signal path uses a digital RGB signal you should avoid any color decoding problems. Otherwise, so long as both source and display are properly configuried and working correctly I don't see that it would make any difference.

Hi all,

Is there any preference as to whether one should select a device to output HDMI RGB as opposed to component HDMI YCbCr (providing the device supports both - see PS3, oppo 970hd etc), when calibrating a system?

If so what is the compromise (if any) with some source devices which only output HDMI YCbCr (ie a Sat Reciever, tosh HDDVD hd-e1 (or ax1 in US I think) etc)

My thinking is since most of the digital displays will output anything (over HDMI) as HDMI RGB, it is better to have the source outputting HDMI RGB too (?) avoiding any color space issues that come from sources mis-matching SD ITU 601 to HD ITU 701 when using HDMI component (thinking of upscaling/upconverting players here). But is it the case?

Many thanks,

Kostas

If your signal path uses a digital RGB signal you should avoid any color decoding problems. Otherwsie, so long as both source and display are properly configuried and working correctly I don't see that it would make any difference.

Hi Tom,

Is there something that could be used to verify that source and display are working correctly? How could this be seen?

Another question about this step in your instructions:
Color
" 1. Point the colorimeter or light meter towards the screen and display a 75% white window. It is important that you use a window, not a full screen.
2. Measure the Y value of white (this is essentially the brightness or intensity of the white window).
3. Display a 75% Red window, and measure the Y value here as well.
You will notice that as you move the Color control up and down, the Y value of Red increases and decreases, but white stays the same.
4. Set the color control at the point where Red measures closest to 21% of the white reading."

I'm using Spyder2, HCFR and GetGray. Sensor points to screen, maybe 20cm distance. I have configured HCFR: Sensor->Calibration->"IRE level images to 75", is this ok or does it matter at all when measuring the above step?

I followed your instructions and used continuous mode in HCRF to measure xyY (looking at values in Measures window) for the 75% white window (Y value was ~5.3) then switched to 75% red window (Y value was ~0.5), but no matter how I moved the Color setting in my HS60 projector it did not seem to make much difference. Maybe moved from 0.4-0.6. Whats wrong here?

I'm using Spyder2, HCFR and GetGray. Sensor points to screen, maybe 20cm distance. I have configured HCFR: Sensor->Calibration->"IRE level images to 75", is this ok or does it matter at all when measuring the above step?

I followed your instructions and used continuous mode in HCRF to measure xyY (looking at values in Measures window) for the 75% white window (Y value was ~5.3) then switched to 75% red window (Y value was ~0.5), but no matter how I moved the Color setting in my HS60 projector it did not seem to make much difference. Maybe moved from 0.4-0.6. Whats wrong here?Do not change that setting to 75. Leave it at its default of 100.

You may be below the threshold at which the sensor can get reliable readings. Try using 100% white and red windows, and position the sensor no more than 18" from the screen.

Although there are no hard and fast rules about this, I would make color adjustments in the following order:

- Color/Tint
- Gray scale
- Color decoding
- Color gamut

Tom if you have a CMS which has RGBCMY controls do you just skip the Color/Tint stage and leave them at unity?? I'm guessing you set brightness and contrast first.

Tom if you have a CMS which has RGBCMY controls do you just skip the Color/Tint stage and leave them at unity?? I'm guessing you set brightness and contrast first.Yes, if the CMS includes a full compliment of controls over saturation, hue, and brightness. For example the Epson 1080p has saturation and hue controls, but no adjustment for color brightness. Thus, you must consider the user Color control.

I deleted the post containing a database of displays with a CMS and added it to the end of the initial article. I also clarified some information about the use of 75% windows for color adjustments.

Do not change that setting to 75. Leave it at its default of 100.

You may be below the threshold at which the sensor can get reliable readings. Try using 100% white and red windows, and position the sensor no more than 18" from the screen.
I bought Eye-One LT because people here seem to think it is much better than Spyder2. Hopefully I did not waste my money, plus I hope it is alot faster than Spydey ;)

Does anybody know if the Sony XBR4/5 has a full CMS?? I don't get my 52" till the start of October when Sony Australia receives their stock :(

Hi Tom, thanks for this great threat and your tips! I am awaiting Spyder2 and downloaded HCFR software and dvd with test images and want to calibrate my Epson TW1000. It will be my first serious calibration attempt. I remember you calibrated him once, have you some specific tips for this projector, or should i simly try follow the instruction on the first site of this threat?

Hi Tom, thanks for this great threat and your tips! I am awaiting Spyder2 and downloaded HCFR software and dvd with test images and want to calibrate my Epson TW1000. It will be my first serious calibration attempt. I remember you calibrated him once, have you some specific tips for this projector, or should i simly try follow the instruction on the first site of this threat?Nothing special. Calibration with its CMS and gray scale controls is straightforward. It has no controls for the color decoder. The upcoming Epson TW2000 UB will have.

Does anybody know if the Sony XBR4/5 has a full CMS?? I don't get my 52" till the start of October when Sony Australia receives their stock :(It does not.

On another subject, I beleive it was Tom that mentioned that my RGB levels (especially Green) were lower than should be necessary for a proper calibration on this unit. The reason they were so low was my method, posted on the forum quite awhile back, by Guy Quo. His method was basically, center Brightness/Contrast, set Red and Blue Offset too low and use Green Offset to set Brightness (make BTB match backround). Return Red and Blue Offsets to default. Then, set Red Gain to highest that doesn't cause clipping. Then use only the Green and Blue Gains, and the Red and Blue Offsets to calibrate. I've always assumed this was correct. I mean Guys knows what he's talking about...right?

Rob

robbyc30,

I was rereading this thread (again) and I came across the quote above. I was wondering if you or anyone else had a link to this method or if you could answer a few questions about it.



1. How do you: use Green Offset to set Brightness (make BTB match backround). Do you put up the pluge pattern (or other - i.e. getgray) and just use the green offset to adjust the brightness of the black?

2. How do you: set Red Gain to highest that doesn't cause clipping. Would you put up 100% stimulus and increase red gain until it starts to drop off in the continuous measures?

3. Is the purpose of this method to get the best range without having the gains and offsets clip? I thought I saw something similar in the Smart III documentation from years ago.

Anyway, sorry if this isn't the right place for this question but I would appreciate any direction.

It does not.

Is it missing CMY controls?

It has no CMS at all so far as I can tell. Just color temp adjustments.

It has no CMS at all so far as I can tell. Just color temp adjustments.

It has RGB gain and bias in the user menu

I don't have a link, but I found a prinout that I will re-type for you. As far as the questions:
1) Yes.
2) I think the way I did it, which I believe is an acceptable method, was to put up a 100IRE screen and adjust the Red Gain until the Red value stops increasing. I actually ended up having to lower mine to -6 I believe.
3) I'm not sure of the benefits of using this method. I've wondered if the end results would be significantly different than just using the Brightness and Contrast settings. I just passed 100 hrs, so at some point I need to do a touch-up, and plan on checking this.

Here's the post from Guy Kuo:

"For most digital projectors which are red limited output, I'd do the following to get contrast and brightness, gains and biases set.

As a preliminary, set contrast and brightness to middle settings. Then go into the grayscale adjustments and use them to get grayscale, white and black correct.

1. Turn red and blue bias a good ways down to intentionally set them too low
2. Set green bias to make the blacker than black stripe match black (digital 16) backround.
3. Return red and blue bias to previous settings and from here on leave the green bias alone!
4. Set red gain to the highest that doesn't cause the top end output to be red deficient. That means the highest setting of red gain that doesn't cause red to clip. You can pretty easily see this by looking for a color shift of the 90, 100, and above white stripes in Avia Pro. Once this is done leave red gain alone.
5. Adjust gray scale using only the green and blue gains for the top end. Use only the red and blue bias controls for adjusting the bottom end of the grayscale. Leave the red gain and the green bias alone while adjusting the grayscale."

Rob



robbyc30,

I was rereading this thread (again) and I came across the quote above. I was wondering if you or anyone else had a link to this method or if you could answer a few questions about it.



1. How do you: . Do you put up the pluge pattern (or other - i.e. getgray) and just use the green offset to adjust the brightness of the black?

2. How do you: . Would you put up 100% stimulus and increase red gain until it starts to drop off in the continuous measures?

3. Is the purpose of this method to get the best range without having the gains and offsets clip? I thought I saw something similar in the Smart III documentation from years ago.

Anyway, sorry if this isn't the right place for this question but I would appreciate any direction.

It has RGB gain and bias in the user menuYes, that's the color temp adjustments.

Yes, that's the color temp adjustments.

Which means I can adjust Grey Scale but that's about it?

Which means I can adjust Grey Scale but that's about it?Yep.

I don't have a link, but I found a prinout that I will re-type for you. As far as the questions:
1) Yes.
2) I think the way I did it, which I believe is an acceptable method, was to put up a 100IRE screen and adjust the Red Gain until the Red value stops increasing. I actually ended up having to lower mine to -6 I believe.
3) I'm not sure of the benefits of using this method. I've wondered if the end results would be significantly different than just using the Brightness and Contrast settings. I just passed 100 hrs, so at some point I need to do a touch-up, and plan on checking this.

Here's the post from Guy Kuo:

"For most digital projectors which are red limited output, I'd do the following to get contrast and brightness, gains and biases set.

As a preliminary, set contrast and brightness to middle settings. Then go into the grayscale adjustments and use them to get grayscale, white and black correct.

1. Turn red and blue bias a good ways down to intentionally set them too low
2. Set green bias to make the blacker than black stripe match black (digital 16) backround.
3. Return red and blue bias to previous settings and from here on leave the green bias alone!
4. Set red gain to the highest that doesn't cause the top end output to be red deficient. That means the highest setting of red gain that doesn't cause red to clip. You can pretty easily see this by looking for a color shift of the 90, 100, and above white stripes in Avia Pro. Once this is done leave red gain alone.
5. Adjust gray scale using only the green and blue gains for the top end. Use only the red and blue bias controls for adjusting the bottom end of the grayscale. Leave the red gain and the green bias alone while adjusting the grayscale."

Rob

Thanks, robby, that is exactly what I was looking for. I appreciate the retyping efforts.

I am still a little confused, though. This seems to be a method to maximize the offsets and gains so there is not clipping of green (on the low end) and red (on the high end). This is similar to the SMART system by Steve Smallcombe that I have read about but never tried. It just seems that only using the green bias to adjust the black level, then bring up the red and blue bias and get to color temp of 6500K. Is there more context? Do you set overall black and white levels again after the color temp is set? I need a little more enlightenment.

On a side note, if these posts seem to be inapproprate for this thread, I would ask that the moderator move them to this thread: http://www.avsforum.com/avs-vb/showthread.php?p=11631891#post11631891

Thanks.

thanks ! I have only two more little questions: how to set right the skin tone correction(i belive it regulates the amouth of green in the picture) and(little off topic) is there a simple rule how to set contrast(i use for this usualy the THX optimizer pattern, but with TW1000 there is huge up and down room in which the pattern still loks right)

thanks ! I have only two more little questions: how to set right the skin tone correction(i belive it regulates the amouth of green in the picture) and(little off topic) is there a simple rule how to set contrast(i use for this usually the THX optimizer pattern, but with TW1000 there is huge up and down room in which the pattern still looks right)This is getting a little far afield from color calibration and moving towards general questions about a specific device. In any case, yes, the skin tone correction just affects the amount of green in the gray scale. If I recall 3 was the most neutral setting.

You look for several things in setting contrast.

Does the set clip whites on the high end? If so, you need to reduce contrast.
Do you see any color shifting at peak output? If so reduce contrast.
Does ordinary viewing cause fatigue or eye strain? If so, reduce contrast.So, the general rule of thumb is to set contrast at the highest level that none of these occur. 35 fL is a good target for CRTs, flat panels, and rear projection. 15 fL is a good target for front projection.

This is getting a little far afield from color calibration and moving towards general questions about a specific device. In any case, yes, the skin tone correction just affects the amount of green in the gray scale. If I recall 3 was the most neutral setting.

You look for several things in setting contrast.

Does the set clip whites on the high end? If so, you need to reduce contrast.
Do you see any color shifting at peak output? If so reduce contrast.
Does ordinary viewing cause fatigue or eye strain? If so, reduce contrast.So, the general rule of thumb is to set contrast at the highest level that none of these occur. 35 fL is a good target for CRTs, flat panels, and rear projection. 15 fL is a good target for front projection.

Can HCFR be used to measure fL values (foot Lambert) or do I need a seperate meter?

I have very big problem with my contrast and I don't know what to blame. I have a bat cave, Stewart Grayhawk RS, Sony HS60 (contr = 57, zoom is at the smallest picture setting), VP30(contr=-15) and even now the picture seems to bright?? This does not seem normal to me, but maybe the HS60 is simply a light cannon?

Can HCFR be used to measure fL values (foot Lambert) or do I need a seperate meter?

I have very big problem with my contrast and I don't know what to blame. I have a bat cave, Stewart Grayhawk RS, Sony HS60 (contr = 57, zoom is at the smallest picture setting), VP30(contr=-15) and even now the picture seems to bright?? This does not seem normal to me, but maybe the HS60 is simply a light cannon?The HS60 is NOT a light canon. It uses a 135W bulb if I recall. For a front projector I don't think you can use HCFR to measure foot lamberts. If someone knows how, then speak up.

If I were you I would purchase an AEMC CA813 light meter, which you can get online for about $150. Then:

Use a test DVD to play a full white window (100 IRE).
Place the meter at the screen facing the projector.
Set the meter to read in Lux.
Use the following formula to determine fL.(Lux/10.76)*screen gain=fL

I am pretty sure that HCFR measures Y candela per square meter (Y=cd/m^2). Doesn't 1 candela / (meter^2) = 1 lux?

I am pretty sure that HCFR measures Y candela per square meter (Y=cd/m^2). Doesn't 1 candela / (meter^2) = 1 lux?

no, lux=lumen/m^2 and is a unit of illuminance. nit=candela/m^2 = lumen/m^2/steradian is a unit of luminance. HCFR reports whatever the probe generates so if it's calibrated in lux, it will report lux, nits it will report nits. AFAIK it does not support any illuminance type meters.

Thanks for the clarification, zoyd.
HCFR reports whatever the probe generates so if it's calibrated in lux, it will report lux, nits it will report nits.
Maybe a dumb question but.....How do I know what units (nits or lux) my eyeone LT is generating? I though it was nits.

Thanks for the clarification, zoyd.

Maybe a dumb question but.....How do I know what units (nits or lux) my eyeone LT is generating? I though it was nits.

the default mode for the probes people are most familar (spyder, display LT, dtp-94, i1pro) is nits. Some have (I think the display LT is like this) an illuminance mode in which you place the probe into an opaque fixture and a different calibration table is loaded which will report in lux.

That's what I thought. Thanks again, zoyd.

Hello you experts. This is probably a dumb question : -) When you use a for example Pantone Eye-One Display LT to calibrate a projector where do you point it? Towards the projector? Towards the screen? If it is towards the screen will it not be a shadow from the measurement probe? Do you angle it so it does not measure its own shadow?

Thanks so much for making this post. I've been searching for a primer on calibration and this was exactly what I needed. Much appreciated.

When you use a for example Pantone Eye-One Display LT to calibrate a projector where do you point it?I pointed it at the screen because I saw others had done the same. If you point it at the PJ I believe you need a light diffuser and I think the one that comes with the LT is not good for that application. Angle it up (assuming the PJ is ceiling mounted) and towards the center.

Color Definitions (HD)
-------------x--------y-------Y
White--------0.313---0.329---1.00
Red----------0.640---0.330---0.213
Green--------0.300---0.600---0.715
Blue----------0.150---0.060---0.072
Cyan---------0.225---0.329---0.787
Magenta------0.321---0.154---0.285
Yellow--------0.419---0.505---0.928
If I'm calibrating a 1080p HD TV (DLP), but using a SD DVD player, should I use these numbers or alternative numbers for SD? Does it make a huge difference if I'm calibrating my HD TV using a SD source versus an HD source (I'll be buying a HD DVD / BR player shortly).

Use these numbers. HD sources will be perfect. SD sources will be slightly oversaturated.

I just finished putting together a spreadsheet that will automatically calculate Delta-E (CIELAB). All you have to do is input the xyY values. I thought that maybe some might find it useful.