Basic Guide to Color Calibration using a CMS (updated and enhanced) - Page 22 - AVS Forum
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post #631 of 1936 Old 02-04-2008, 09:20 AM
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Tom, as always, thanks for answering.

Quote:
Originally Posted by TomHuffman View Post

The gamma is virtually identical in the before/after.

In the "after" .chc the gamma curve, due to contrast increase, moved a bit towards to 2.3; is that normal?

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Originally Posted by TomHuffman View Post

There's still excess blue at the high-end.

To get the blue in place on high IREs, it will undersature the Blu in the mids. Should I go for it? (I thought the way to go, was to sacrifice high IREs in favour of mids...)

BTW, don't know if this is could be the cause of oversatured blu, but I've skipped the Tint\\Cyan adjustment in the calibration process, going for a Cyan adjustment in the "Hue adjustment" section of the guide... was it a wrong move?



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Originally Posted by TomHuffman View Post

The before HCFR file and the CIE before chart you show in line are not the same, so I don't know how to evaluate this. Nothing you did should have changed the red primary.

They're the same, the only perceptual difference is due to HCFR's .jpg rendering... it looks like the jpeg CIE chart is a bit squeezed on the left/right sides, but the values inside are the same.

Having said so, you can notice that in the "Pre" chart the red is in place, while in the after it is outside the reference. Contrast increase can push the red outside of the reference?
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post #632 of 1936 Old 02-04-2008, 09:26 PM
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Quote:
Originally Posted by TomHuffman View Post

I'd say worthless describes it pretty well. You can move the color points with it some, but it screws up the gray scale.

Tom,

What about the NEC (plasma) CMS? Any good?


thx

bob
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post #633 of 1936 Old 02-04-2008, 11:59 PM
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Basically this are steps for calibrating:

1) Adjust brightness/contrast->gamma
2) Set color amount
3) Adjust tint
4) Adjust grayscale
5) Adjust color decoding/hue/saturation

Once done start again, but I'm unsure if it correct to start from n°1 or ???

Moreover, what if point n° 3 (Adjust tint) is skipped, delaying cyan adjustment in point n° 5??
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post #634 of 1936 Old 02-07-2008, 02:35 AM
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Semi OT: Can someone underline why TV broadcasted channels (Aerial/Satellite) show so big differences between each other, particullarly on the color side?

Shouldn't they adhere to the same standards?
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post #635 of 1936 Old 02-07-2008, 05:18 AM
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There are two things.

First is that sometimes the shows have their colours adjusted on purpose, CSI Miami is the best example of this.

The second reason is that the local technicians need to mix in commercials, an other programming with what they receive from the network so it's likely that when they do that they don't always adjust for different material, e.g. SD commercials mixing with HD TV shows.
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post #636 of 1936 Old 02-07-2008, 07:33 AM
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I'd like to stretch one aspect of Tom's guide, that probabily due to site's unavailability was left over:

At a certain point Tom suggests to adjust Cyan on it's proper position on the CIE chart, using the tint control; further on, in the guide, we are told to adjust colors according to their respective position in the CIE chart.

At this point it looks there could be a calibration-step overlap: Cyan could be adjusted either with tint control or with color controls.... why is Tom suggesting to adjust Cyan using the tint control?

If skipping that step, leaving the tint control untouched, does it change something?
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post #637 of 1936 Old 02-07-2008, 08:00 AM - Thread Starter
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The goal is to get Cyan right. It doesn't matter which method you use to get there. The vast majority of displays will only have a Tint control, but if you also have a Cyan Hue control then use that or just use the Tint control. Either is fine.

Quote:
Originally Posted by blutarsky View Post

I'd like to stretch one aspect of Tom's guide, that probabily due to site's unavailability was left over:

At a certain point Tom suggests to adjust Cyan on it's proper position on the CIE chart, using the tint control; further on, in the guide, we are told to adjust colors according to their respective position in the CIE chart.

At this point it looks there could be a calibration-step overlap: Cyan could be adjusted either with tint control or with color controls.... why is Tom suggesting to adjust Cyan using the tint control?

If skipping that step, leaving the tint control untouched, does it change something?


Tom Huffman
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post #638 of 1936 Old 02-07-2008, 08:50 AM
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Quote:
Originally Posted by TomHuffman View Post

The goal is to get Cyan right. It doesn't matter which method you use to get there.

Is it important to adjust it following your sequence or it can be adjusted later in the "color decoding\\hue\\saturation" step?
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post #639 of 1936 Old 02-07-2008, 09:46 AM - Thread Starter
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Quote:
Originally Posted by blutarsky View Post

Is it important to adjust it following your sequence or it can be adjusted later in the "color decoding\\hue\\saturation" step?

http://www.avsforum.com/avs-vb/showp...&postcount=598

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post #640 of 1936 Old 02-07-2008, 10:14 AM
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post #641 of 1936 Old 02-12-2008, 04:52 AM
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Hi! I`ve been trying to calibrate my RS-1 with HCFR and a Display LT probe. Greyscale is ok, with a dE mostly less than 2. But I`m struggeling with the gamma curve. From different reviews I have read that the RS-1 gamma curve is very good OOTB. "Normal" seems to be at about gamma 2.4. But mine is about 2 in the low parts of the curve, and slopes down to about 1.8 at the high parts.

First I followed this guide to set black and white level, but I noticed that when calculating the black level at 10% as 0.63% of white at 100% I get a much lower black level than when watching the pluge pattern on the AVS test disc. So I used the pluge pattern. This gave about 0.53 NITS at 10%. Calculated it should have been 0,63% of 51 NITS = 0.32 NITS. Seems to me that if I want to get the gamma curve closer to average 2.2 I have to reduce both brightness and contrast??

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post #642 of 1936 Old 02-12-2008, 01:53 PM - Thread Starter
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Using direct measurement to set brightness assumes a gamma in the 2.2-2.5 range. If yours is 2.0-1.8, then you have other problems. That is too low. The 0.63% of peak white assumed a 2.2 gamma, which you don't have, so this method won't work.

Quote:
Originally Posted by Gunnar View Post

Hi! I`ve been trying to calibrate my RS-1 with HCFR and a Display LT probe. Greyscale is ok, with a dE mostly less than 2. But I`m struggeling with the gamma curve. From different reviews I have read that the RS-1 gamma curve is very good OOTB. "Normal" seems to be at about gamma 2.4. But mine is about 2 in the low parts of the curve, and slopes down to about 1.8 at the high parts.

First I followed this guide to set black and white level, but I noticed that when calculating the black level at 10% as 0.63% of white at 100% I get a much lower black level than when watching the pluge pattern on the AVS test disc. So I used the pluge pattern. This gave about 0.53 NITS at 10%. Calculated it should have been 0,63% of 51 NITS = 0.32 NITS. Seems to me that if I want to get the gamma curve closer to average 2.2 I have to reduce both brightness and contrast??


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post #643 of 1936 Old 02-13-2008, 12:11 PM
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Hello all,

This is a great thread and digesting all the information is certainly educational.

I have a Samsung LNT-4061 LCD that I am thinking of calibrating using Tom's guide in the first post but I just have a few basic questions before taking the plunge.

(1) I can see that the Display 2 is the preferred colorimeter but I'm wondering how does one attach it to the display. I don't own a tripod - does it come with suction cups and are those ok for an LCD?

(2) I have the new Avia II disc and I'm well versed in all the patterns, is this enough for the calibration dvd or should I use Tom's specific dvd?

(3) Samsung has basic controls for contrast, brightness, color, tint/hue, sharpness. One question I have is that the tint/hue control is labeled G on the left and R on the right. Does this mean that it is not set up to control Cyan but Yellow instead?

(4) The Samsung also has some advanced controls for gamma and grayscale which I understand fine but it has one thing called My ColorControl which contains a list of 4 colors (pink, white, blue, green). The manual only says that it "darkens or lightens" the color. Using patterns, I can see white affects the entire grayscale which make sense but blue/green don't do anything on the color decoder pattern so it does not seem to be affect the brightness. Does anyone have any experience with what these do?

thanks so much for any help you can offer,


--tom
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post #644 of 1936 Old 02-14-2008, 08:10 AM - Thread Starter
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It has suction cups and a counterweight.

The consumer version of Avia uses grayscale patterns that are not completely neutral gray. You can use my DVD. GetGray also offers a nicer one for $25.

No, it is a normal Tint control.

Leave the MyColorControl alone.

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Originally Posted by thomasl View Post

(1) I can see that the Display 2 is the preferred colorimeter but I'm wondering how does one attach it to the display. I don't own a tripod - does it come with suction cups and are those ok for an LCD?

(2) I have the new Avia II disc and I'm well versed in all the patterns, is this enough for the calibration dvd or should I use Tom's specific dvd?

(3) Samsung has basic controls for contrast, brightness, color, tint/hue, sharpness. One question I have is that the tint/hue control is labeled G on the left and R on the right. Does this mean that it is not set up to control Cyan but Yellow instead?

(4) The Samsung also has some advanced controls for gamma and grayscale which I understand fine but it has one thing called My ColorControl which contains a list of 4 colors (pink, white, blue, green). The manual only says that it "darkens or lightens" the color. Using patterns, I can see white affects the entire grayscale which make sense but blue/green don't do anything on the color decoder pattern so it does not seem to be affect the brightness. Does anyone have any experience with what these do?


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post #645 of 1936 Old 02-14-2008, 04:51 PM
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[/b]
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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 GretagMacbeth i1Pro, though it can be a pain to use. A much less expensive option that is only a little less accurate is the GretagMacbeth 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. I have the SpyderII
  • Calibration Software. You need this to interpret the data that the meter receives. Aside from the very expensive professional tools, there are 2 good choices for amateurs: HCFR Got thisand CalMan. HCFR is freeware. CalMan is commercial software that costs about $150, depending on selected 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. Avia Guide to Home Theater works well and sells for about $30. An even better choice is the GetGray disk, which can be downloaded and burned to DVD for about $25. Finally, I have created my own freeware calibration disc which I have burned and have working perfectly...great disc, thanks!that provides all the patterns necessary for the steps in this guide. See below for a download link.
  • Light Meter (optional). I don't have this....really not necessary right?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 inexpensive standalone tool and 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 generally referred to in 3 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 gray from vary dark scenes to very bright scenes. If the display can't do this, then it will add a color cast to the display that can make images look very unnatural. Calibrating the gray scale has been discussed extensively elsewhere.
  • Color Decoding. This is the display's ability to properly render the relative brightness of the primaries and hue of the secondaries. All commercial displays include a Color and Tint control. These are basically Color Decoding controls, though their effectiveness is limited because Color adjusts the brightness of ALL colors and Tint effects only the hue of cyan. The problem is that displays all-too-often have color decoding errors that effect the colors differently. Thus, you can adjust Color/Tint to get the correct brightness of blue, for example, and the correct hue of cyan, but the brightness of green and red can still be inaccurate. You could adjust the color control for red, but then blue and green would be inaccurate. See the problem? A full set of color decoding controls addresses this problem.
  • Color Gamut. This is the display's ability to correctly render the saturation and hue of all of the colors, typically represented as the primaries (red, green, and blue) and the secondaries (cyan, magenta, and yellow). In recent years it seems that digital displays have gotten increasingly inaccurate in this respect. The only way to fix it is with a CMS. This can make a profound difference to the performance of the display, but most do not offer a CMS and of those that do not all work properly.
It is important to understand that these three measurements of color accuracy are for the most part independent. You can have good gray scale tracking and poor color decoding. You can have good color decoding and a very 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 coordinates that plot out the position of a color on a CIE chart, which graphically represents the established definitions of the basic colors. Y is the brightness of the color. This is not plotted on the CIE chart. So does this mean in HCFR I check the little box that says "xyY"?
  • Color Saturation - the colorfulness of the color. A color's saturation is measured on the CIE chart as the distance from the white point.
  • Color Hue - the purity of color. A color's hue is measured by its angle to the white point.
  • Color Brightness - the luminance of color. A color's brightness is measured by how much light it projects.
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


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

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

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

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.
  1. Select a target gamma. How do I do this? What button do I press in HCFR? My DLP has no gamma adjustment.I cannot think of any reason to choose any gamma other than 2.2 or 2.5.*
  2. Measure the peak output if you have not already using a 100% white window or field.What buttons in HCFR do I press to measure this?
  3. Display a 10% window or field.
  4. Adjust the Brightness setting so that this test pattern measures as close as possible to 0.63% of peak white (2.2 gamma) or 0.32% (2.5 gamma).So, if I'm shooting for 2.2, I multiply my peak white figure by what, 1.63? I'm not a math major...so don't laugh.
*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 prefer a 2.2 gamma for its excellent shadow detail, but this is largely a matter of personal preference. However, I wouldn't go above 2.5 or below 2.2.

Setting White Level (Contrast)

The Contrast control determines how much 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 or 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 grayscale 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: 35 fL
  • Plasma: 35 fL
  • LCD flat panel: 50 fL
  • Digital rear projection: 35 fL
  • Digital front projection: 15 fL
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 fL or in cd/m2 (candelas per meter squared or nits). If it measures in nits, just multiply the peak output (100% Y) by 0.29 to get fL. Nits and fL are a measure of luminance, which is an emission or reflection of light from a flat, diffuse surface. All colorimeters and spectroradiometers measure luminance.I have a DLP. What button(s) do I press on HCFR to measure fL? If my fL turns out to be 30fL, do I turn contrast up or down to get to 35fL?

If you have a front projector, it is a little more complicated. First, you really need a good illuminance meter for this. Illuminance is a measurement of light that falls on or illuminates surfaces. Thus, 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. Unless you have a very expensive luminance meter, such as the Konica Minolta LS-100/110, you will 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 then multiply by the real* gain of the screen. This gives you fL for front projectors.

* 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.

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 2 test patterns for setting sharpness on the calibration DVD.

Setting Color/Tint

The standard method for doing this involves looking at a SMPTE color bar 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
  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).What button do I press on HCFR to do this?
  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.The math here is a little easier I think. This time I just multiply by .21, right?
Note: It is not really important that you specifically use a 75% window. You can use 100% intensity windows if you prefer. Just make sure that whichever you use, you use the SAME intensity window for white AND red.

Tint
  1. Point the colorimeter towards the screen and display a 75% window of Cyan.
  2. Use the software controls to plot the Cyan reading on a CIE chart.What button to I press on HCFR to do this?
  3. Adjust Tint up or down until the reading places the measured point 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)Does HCFR read in real time?.
Adjusting the gray scale

Briefly, gray scale adjustment simply involves adjusting specialized controls By this I assume you mean in the service menu.that allow a display to track a neutral gray throughout its entire range from the blackest black to the whitest white.

Unlike a good CMSYou are using "CMS" here as a generic term for video display?, which is rare, virtually all displays have gray scale controls. Sometimes they are in the user menu, but more 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 0.313/0.329. The calibration software will provide these raw numbers and some type of graphical representation of RGB relative to the target white point.

To calibrate the gray scale:
  1. Aim the meter at the display.
  2. Select a 90 IRE window on the calibration DVD.
  3. Adjust the RGB Contrast Which on my Mitsubishi DLP I believe are the Gain controls labeled GBL, BRL and GGL...the "L" is for "Low" color temp...Are the "RGB Contrast" controls the same as "Gains"?controls until RGB is balanced at 90 IRE or until you read 0.313, 0.329..313 is x and .329 is y?
  4. Select a 30 IRE window from the calibration DVD and use the RGB Brightness I don't think my Mits has controls for these. Are these the Gains? controls to balance RGB or achieve 0.313, 0.329.
  5. Repeat the last two steps as many times as necessary until both the 90 IRE window and the 30 IRE window measure neutral gray. This may take several sets of measurements.
  6. Finally, take an entire series of gray scale measurements at 10 IRE intervals from black to 100 IRE to ensure that the display tracks gray accurately throughout the entire range.
Sometimes you may find that even though 90 and 30 IRE are neutral gray, the mid range 50-70 IRE 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. How do I "focus on the mid range"? Just concentrate on, say, 50-70 IRE?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 OK, sorry, I think this answered my previous question...and Brightness, Biases, Offsets, and Cuts are for adjusting the dark end of the gray scale.

Adjusting the Color Decoder

The display's color decoding performance is not for the most part* recorded on the CIE chart, so you must use a method similar to what is described above about setting Color. A full-featured CMS will have controls for Saturation, Tint, and Value (sometimes referred to as Lightness or Brightness) of RGBCYM. Some CMS's do not have a Value adjustment, which probably means that this display does not have color decoding adjustments. However, some displays that do not have a CMS at all do have dedicated color decoding controls in the service menu (e.g., Sony CRTs).
  1. Point the meter towards the screen and display a 75% white window.
  2. Measure and record the Y value. Again, I have no idea what to hit in HCFR to take any of these measurements.
  3. Display a 75% Green window.
  4. Measure and record the Y value.Same
  5. Repeat the previous 2 steps for Blue.
  6. Adjust the Value setting in the CMS up or down so that Green is as close as possible to 71% (multiply reference white number by .71? of the reference white and Blue is as close as possible to 8% Mulitply by .08?to reference white.
  7. Since you already set Red with the Color control, no further adjustment should be necessary.
Note: Some displays will include color decoding adjustments for hue as well as brightness. These are essentially the same as the main Tint control, except they affect magenta and yellow, instead of cyan. For example, Sony CRTs offer RYR (red brightness), RYG (red tint), GYG (green brightness), and GYR (green tint) in the service menu. Red tint adjusts the hue of magenta. Green tint adjusts the hue of yellow. Use these as enhancements to the main Color/Tint control to achieve virtually perfect color decoding. I have "Perfectcolor" on my Mits. This is not in the service menu but in the user menu. This to me appears to be just a color saturation or brightness control. Do I use this here? My model unfortunately does not have "Perfect Tint"

* Since part of the color decoder performance is measured as the hue of the secondaries, this is measured by the CIE chart. Simply address this issue as part of the hue/saturation adjustments discussed below. Also, adjustments to the gray scale will affect the hue of the secondaries. This is one of the reasons you should perform gray scale calibration prior to considering color decoding.

Adjusting Hue and Saturation
  1. Point your colorimeter towards the screen and display a 75% Red window.
  2. Use the software controls to plot the Red reading on a CIE chart.What buttons in HCFR do I push to measure this?
  3. Adjust the Saturation and Hue controls in the CMS until measured Red lines up as close as possible to the reference point for Red on the CIE chart (It is helpful if the software has a continuous reading mode so your changes to Red can be viewed on the CIE chart in real time).
  4. Repeat this process for the remaining primary/secondary colors. You probably won't be able to get all colors lined up perfectly, but get them as close as you can.
  5. It is important to understand that when you make these adjustments, only the xy points should change. However, some poorly designed CMSs are such that as you change the xy values to get correct hue/saturation and a good looking CIE chart, the Y value will change as well. It is very important that you check the Color Lightness, which does not show on the chart at all, after making these changes. Otherwise, you could have made the color worse without knowing it.
Note: 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.

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 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 90/30% windows and fields for initial grayscale adjustment
  • 100% RGBCYM patterns in windows and fields
  • Just below white and pluge patterns for setting Contrast and Brightness (though I recommend you use the method I describe above for most applications).
  • A couple of test patterns for checking sharpness.
You navigate through the individual patterns by pressing the Chapter Forward button.Your DVD is awesome. I just hope there is a "HCFR/AVS calibration for DUMMIES" manuscript posted at some point.

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
Download generic DVD files

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 gray scale controls easily identifiable and accessible in the user menu, but they 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 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 (my BMR, BMB and BMG in the service menu.and dark ends My OFG, OFR and OFB in the service menu.of the gray scale, and at least 2 of the following I have to other sets of adjustments in the service menu that address this I believe.
- color decoding adjustments I think these are my gain RGB gain controls in the service menu
- saturation adjustments for RGBCYMI think this is my "Perfectcolor" adjustments.
- hue adjustments for RGBCYM I thnk I am SOL here...any alternatives?

Ideally, you want to have all four.

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

Front Projection
  • Yamaha DPX-1300 (DLP)
  • Sharp XV-Z20000 (DLP)
  • Sharp XV-Z12000 Mk II (DLP)
  • Sharp XV-Z3100 (DLP)
  • Sharp XV-Z3000 (DLP)
  • Sharp DT-500 (DLP)
  • Marantz VP4001 (DLP)
  • Epson Home Cinema 1080 UB (LCD)
  • BenQ W9000/10000 (DLP)
Rear Projection
  • Mitsubishi 1080P Diamond Models (DLP/LCD)*
  • Samsung (DLP)
Flat Panel
  • Toshiba Cinema Series (LCD)
  • Fujitsu (Plasma)*
  • Hitachi Director Series (Plasma)
* Includes adjustments for color decoding and hue, but not for saturation

Should I post my results for evaluation here after I am finished or the HCFR thread?


Thanks to all for their help!
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post #646 of 1936 Old 02-14-2008, 08:04 PM
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Thanks very much for your quick reply Tom.

I picked up an Eye-One Display LT this evening so it looks like I know what I'll be tinkering with this weekend.

I will see about burning a copy of your dvd. Do you know if Avia II suffers from the same color leakage as the original Avia? I recall way back when I bought it in 2001 that I was told one way to get around that was to turn down the color control to 0 before looking at any grayscale patterns.

Thanks for the tip on MyColorControl. I figured that it should be avoided since all reviews have stated that they couldn't figure out what it does exactly - so they all left it alone. Out of my own curiosity though, I am wondering if anyone knows what the green and blue controls under that menu do. If they really don't do anything, is it simply a marketing tool by Samsung? Or could they be affecting the color saturation and hue (the Avia patterns show that they have no affect on brightness at least in Movie mode with a 1080p signal over the HDMI input - I do realize that sometimes these type of features are only active for certain types of modes and inputs).

I was also told that Samsung LCDs don't tend to have color management controls accessible in the service menu. Does anyone know if this is the case? I was not planning on entering the service mode since grayscale and gamma controls are at the user level. At this point, I'm looking just to try to set the gamma and calibrate the grayscale. I figure other than the standard color/tint controls, the best I can do is use the software to see how well the set does with the color points.

I should also say that your concise description about color at the beginning is the best summary I've read. I've spent the past few weeks reading various things which helped me understand things but your description really crystallizes it.

many thanks,


--tom
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post #647 of 1936 Old 02-14-2008, 09:21 PM
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I did get into HCFR tonight and just started winging it. Not the best way to begin, but it's a start. I got all the RGB levels pretty equal except for the low end (between 0 and 30 IRE). They are out of whack. Most of my playing in the service menu has been trial and error.

Says my gamma is at 2.11. I guess that's low from what I've read, but I have no idea how to change it to 2.2.

I tried many of the calculations in the Guide (this thread) but couldn't figure anything out. Really need someone to hold my hand and walk me through it.

I'll mention when I first measured (before using HCFR and the SpyderII, my grayscale was fairly flat BUT my RGB levels were way off. They were all flat, but the green was way up there, and the blue was really low. They are all on top of one another now....but the low end of the grayscale got thrown off a bit (as did the RGB levels from 0 to 30).

Having said all that, the picture looks phenominal now, watching the test videos on DVE HD. Really nice.
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post #648 of 1936 Old 02-14-2008, 10:43 PM
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wow thanks, nice guide
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post #649 of 1936 Old 02-15-2008, 12:43 AM
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Thanks Tom!
I notice that another RS-1 owner (Rayjr) get a much flatter gamma at 2.2. I don`t know his screensize, but he has about 40 nits at 100%, while I have about 51 nits. So I`ll try to reduce contrast and adjust brightness, and see if the gamma curve improves.

Gunnar
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post #650 of 1936 Old 02-16-2008, 04:29 AM
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Greetings.
Till now I've been performing measurements at night, in complitely dark conditions, with the EYEONE Display LT sensor faceing the plasma screen, without adhesive tape, to avoid light interference.

Wishing to do some testing in daytime, I'm asking if are there some steps I should take (adhesive tape) to avoid light disturbing the sensor, or if it is unnecessary, considering that the sensor is facing/attached to the screen...
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post #651 of 1936 Old 02-16-2008, 09:44 PM
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Hey Tom... Thanks for the Guide !!! Not sure I could have made it through my first HCFR calibration without it, and I was very happy with the end results.

I notice that you update the guide on occasion and was wondering if you could address windows versus full field measurements in the guide (or here in the thread) ? Specifically, it seems that luminance values could be significantly different depending on whether a full field or window is displayed. I believe this is true of plasma technology, but was wondering if it also applies to other technologies ? If so, it would impact the contrast setting if targeting a specific luminance value.

Sean
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post #652 of 1936 Old 02-16-2008, 10:56 PM
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Quote:
Originally Posted by legierk View Post

I did get into HCFR tonight and just started winging it. Not the best way to begin, but it's a start. I got all the RGB levels pretty equal except for the low end (between 0 and 30 IRE). They are out of whack. Most of my playing in the service menu has been trial and error.

Says my gamma is at 2.11. I guess that's low from what I've read, but I have no idea how to change it to 2.2.

I tried many of the calculations in the Guide (this thread) but couldn't figure anything out. Really need someone to hold my hand and walk me through it.

I'll mention when I first measured (before using HCFR and the SpyderII, my grayscale was fairly flat BUT my RGB levels were way off. They were all flat, but the green was way up there, and the blue was really low. They are all on top of one another now....but the low end of the grayscale got thrown off a bit (as did the RGB levels from 0 to 30).

Having said all that, the picture looks phenominal now, watching the test videos on DVE HD. Really nice.

I have a mitsi DLP as well and my gamma is in the 2.1 range as well. From what I can tell, there isn't a way to boost it. As far as the below 30 goes, if you're tracking even from 30 - 100, then leave it. The spyder doesn't read well below 30 anyway, so you really can't trust what it's reporting at that level. From what I've read and been told, you need much more expensive equipment to get an accurate reading below that anyway.
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post #653 of 1936 Old 02-17-2008, 04:19 AM
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Thanks for the response. After my initial calibration I nhaven't had time to go back and re-run any tests.

Does anyone have the HCFR guide translated into English perhaps as an Office or PDF document? (wrong forum I know)
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post #654 of 1936 Old 02-19-2008, 02:35 AM
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Hi all, first of all my apologies for my very bad english, please, take a little patience.

Now to the work... I'm trying to calibrate my front projector for SD viewing...


The actors

- ProjectionDesign Action Model Two DLP front projector. 1280x720 native resolution, DVI plug, 4x speed color wheel with 7 color segments (6 plus additional dark green segment), by the way, the red segment is bigger than the other ones as you can see in the following image taken from Cine4home site:


- Denon 2930. SD DVD source with Reon chip, upscaling to 1280x720 via HDMI-to-DVI cable transmitting the color with RGB because the projector doesn't use YPbCr with its DVI plug.

- Spyder 2 probe. Yes, I know is not the more accurate probe specially on lower intensities.

- HCFR v2.0.1 software.


The method

1) I've tried to set brightness as Tom recommends so I ended choosing a "video 1" gamma curve from my projector menu and put a 100% Grey Window, started taking measures and observing the Y data (around 52), after that, I've put a 10% Gray window, started continuous measures and moved brightness master control until Y data was around 0,32 (that is a 0.63% of 52). Is this correct?

2) Contrast control. I don't have a luxmeter but the HCFR software can show you the measure in ftL units so I've put a 100% Gray Window and started taking continuous measures and changing contrast master control until I had around 15 ftL.

3) Colors. Taking measures from primaries and secondaries. I can't change the primaries or secondaries locations due to lack of CMS in the projector menu, even the color master control is disabled when you're using the DVI connection (I know its purpose is for color saturation and not for changing the primaries location) but the Denon 2930 has a "hue" picture adjust parameter that moves the secondaries location unfortunately here I'm lost because I have to make a choice: What is preferable: Good yellow, Cyan or Magenta??

Finally, I moved the Denon hue control to +6 in order to minimize the Cyan deltaE but that takes my Yellow to a very bad deltaE of 41 (at least from the CIE triangle view). You can take a look to the CIE triangle at my attachment (HCFR file).


After these steps I started again with the step 1 one or two times more, ended up with a gamma curve of 2.15 and finishing the calibration journey making grey scale RGB adjustments with continuous measures, unfortunately the RGB levels graph that you see in my attachment is *not* the last achieved because it was too late for me (01:30am and working next day) so please don't make comments about.

Any ideas/comments?

As soon as I finish with the grey scale RGB adjustments I will post it.

Many thanks in advance!!

 

PD-Denon-v2.zip 4.880859375k . file
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post #655 of 1936 Old 02-19-2008, 06:26 PM
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Tom,

If setting tint/hue to match the cyan color point a hard and fast rule? Is there any reason that one would not want to try and minimize the errors for all the secondaries. I spent the weekend using your guide/dvd, HCFR and an Eye-One Display LT to calibrate our tvs. Fun stuff. But with no CMS on any of the tvs, I noticed that tint/hue moves the secondary color points along the triangle. In one case, when cyan is correct, yellow is way too red. But if I adjust it so cyan is off a bit I can get yellow closer to green and make magenta spot on. So, I'm just wondering if there is a logical reason that you chose cyan and if I should stick with making cyan accurate no matter what happens to the other secondaries.

Also, you mention that a 10 percent gray window should be .63 percent of the luminance of the 100 percent white window. This assumes a gamma of 2.2. I noticed on all 4 tvs (3 CRTs and one LCD) that none of them tracked gamma at 2.1. The Samsung LCD is close at 2.1 but it's response is not flat. It's lower at the low end IRE (1.9) and a bit higher at the high end IRE (2.3). I've lowered the Samsung gamma setting down to -3 to get it where it is now. What else can one do to fix gamma? And on the CRTs - why would the gamma response be down near 1.8 - I thought CRTs naturally have a gamma response of 2.2 or perhaps it is not meaningful to look at the gamma data on a CRT. In any event, I uses the Avia II's black level patterns to set black level.

Finally, is there an easy formula for figuring out a percent of over-luminance for each color (i.e. the dreaded red push) given all the Y data collected?

many thanks,


--tom
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post #656 of 1936 Old 02-19-2008, 07:26 PM - Thread Starter
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Quote:
Originally Posted by thomasl View Post

If setting tint/hue to match the cyan color point a hard and fast rule? Is there any reason that one would not want to try and minimize the errors for all the secondaries. I spent the weekend using your guide/dvd, HCFR and an Eye-One Display LT to calibrate our tvs. Fun stuff. But with no CMS on any of the tvs, I noticed that tint/hue moves the secondary color points along the triangle. In one case, when cyan is correct, yellow is way too red. But if I adjust it so cyan is off a bit I can get yellow closer to green and make magenta spot on. So, I'm just wondering if there is a logical reason that you chose cyan and if I should stick with making cyan accurate no matter what happens to the other secondaries.

If the grayscale is accurate, the secondaries should be close. In the great majority of cases, the center setting (or very close to it) will be correct. If the grayscale is correct, but the hue of secondaries are still way off with Tint set at its center setting, then its a color decoding error. Usually, the Tint control will have the most immediate effect on cyan, but also on the other secondaries as well, as you saw. If you have color decoding controls, then the Tint control is the ONLY way to adjust cyan. If you don't, then, yes, using the Tint control to minimize dE for all 3 secondaries would probably be ideal. In a majority of cases getting cyan right will have this effect anyway.

You are not the first person to ask this question. I have re-written the sections on setting brightness and Tint to clarify the process.

Good primary lightness is +-5%.

Tom Huffman
ChromaPure Software/AccuPel Video Signal Generators
ISF/THX Calibrations
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Tom, many thanks for your comments.

I will set the Denon hue setting at 0 and I will make grey scale adjustments as usual before starting to play with secondaries.

Keep up the good work!!

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Many thanks Tom for the comments on the secondaries.

Do you have any comments on what to do with sets that do not hold black level across picture intensities? One of our CRTs suffers badly from this. It seems like it is a deliberate feature that Toshiba added and I can't find any way to turn it off in the service manual and there is no user control for it either. Do you still recommend setting the brightness as specified or is a compromise setting a better solution?

I figured I'll also share my technique for setting contrast/brightness/grayscale/color/tint. Since I assumed most sets grayscale was way off (which they were), I first went in and got the grayscale within the ballpark. Once it was close, I then went in and did contrast/brightness. I then looped back and forth doing grayscale -> contrast/brightness -> grayscale, etc. until they all zeroed in. When I was satisfied with those, I then moved onto color/tint. Once I did those, I then went back and re-checked grayscale/contrast/brightness. I think in all cases (which is what I expected), color/tint didn't have any measurable affect on the other settings. I then did sharpness which didn't seem to have any affect on the other settings either.


--tom
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Quote:
Originally Posted by thomasl View Post

I figured I'll also share my technique for setting contrast/brightness/grayscale/color/tint. Since I assumed most sets grayscale was way off (which they were), I first went in and got the grayscale within the ballpark. Once it was close, I then went in and did contrast/brightness. I then looped back and forth doing grayscale -> contrast/brightness -> grayscale, etc. until they all zeroed in. When I was satisfied with those, I then moved onto color/tint. Once I did those, I then went back and re-checked grayscale/contrast/brightness. I think in all cases (which is what I expected), color/tint didn't have any measurable affect on the other settings. I then did sharpness which didn't seem to have any affect on the other settings either.

And what about the gamma curve menu control for all those fortunates that have it?

What would be your methodology?...

1- Set the gamma closest to 2.2
2- Adjust grayscale
3- Set Brightness/Contrast
4- Color/Tint
5- Return to 2 until satisfied

or...

1- Adjust grayscale
2- Set the gamma closest to 2.2
3- Set Brightness/Contrast
4- Color/Tint
5- Return to 1 until satisfied

or anything else...?

Regards.
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post #660 of 1936 Old 02-20-2008, 07:07 AM
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From Tom's original guide (first post in this thread)

Quote:


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 decoding
- Color gamut

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

The important bit here is to iterate. Each adjustment can influence the others, my approach is to go a bit slow and don't aim for total perfection in the first round. I try to do coarse adjustments first, then cycle back to refine.

Roo
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