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05-25-07, 07:15 PM
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AVS Special Member
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Basic Guide to Color Calibration using a CMS (updated and enhanced)
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
First, some basic principles and terminology. Color performance is measured in two ways:
Terminology
Saturation   Hue  Brightness  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 Code:
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
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:
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:
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:
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  Example 2: Saturation change  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.
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.
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
Tint
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:
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)
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.
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:
I have provided the necessary DVD files in 2 formats:
Download Nero image Download generic DVD files Download Nero image in PAL format 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:
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
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Tom Huffman ISF Calibrations/ChromaPure Software Rockville, MD Last edited by TomHuffman; 01-18-10 at 10:23 AM.. |
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05-26-07, 01:13 AM
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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.
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Tom Huffman ISF Calibrations/ChromaPure Software Rockville, MD Last edited by TomHuffman; 05-26-07 at 01:41 PM.. |
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05-26-07, 08:47 AM
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Thanks. |
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05-26-07, 05:40 PM
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Really nice guide Tom, I have one question.
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05-26-07, 05:46 PM
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Tom Huffman ISF Calibrations/ChromaPure Software Rockville, MD |
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05-26-07, 06:19 PM
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 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. Last edited by zoyd; 05-26-07 at 06:25 PM.. |
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05-26-07, 07:18 PM
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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/showt...&#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. Last edited by krasmuzik; 05-26-07 at 07:57 PM.. |
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05-26-07, 08:17 PM
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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.
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05-26-07, 08:32 PM
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I previously did some formal measurements on 2 displays. http://www.avsforum.com/avs-vb/showt...&#post10214658 http://www.avsforum.com/avs-vb/showt...&#post10221787
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Tom Huffman ISF Calibrations/ChromaPure Software Rockville, MD |
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05-26-07, 09:40 PM
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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* Last edited by zoyd; 05-26-07 at 10:12 PM.. |
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05-27-07, 02:08 PM
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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. Last edited by krasmuzik; 05-27-07 at 02:13 PM.. |
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05-27-07, 03:38 PM
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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. |
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05-27-07, 04:05 PM
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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?
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Tom Huffman ISF Calibrations/ChromaPure Software Rockville, MD |
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05-27-07, 04:22 PM
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05-27-07, 05:31 PM
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05-27-07, 05:32 PM
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If you are interested in this stuff, you might consider investing in a display that offers more control over the image quality.
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Tom Huffman ISF Calibrations/ChromaPure Software Rockville, MD Last edited by TomHuffman; 05-27-07 at 05:53 PM.. |
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05-27-07, 05:34 PM
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Tom Huffman ISF Calibrations/ChromaPure Software Rockville, MD |
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05-27-07, 06:09 PM
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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? |
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05-27-07, 06:42 PM
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Thanks again for the help. Last edited by angryht; 05-27-07 at 06:57 PM.. |
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05-28-07, 02:23 AM
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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. Last edited by krasmuzik; 05-28-07 at 02:33 AM.. |
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05-28-07, 12:45 PM
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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.
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Tom Huffman ISF Calibrations/ChromaPure Software Rockville, MD |
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05-28-07, 01:06 PM
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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. Last edited by krasmuzik; 05-28-07 at 01:28 PM.. |
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