HCFR - Open source projector and display calibration software - Page 141 - AVS Forum
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post #4201 of 4209 Old Yesterday, 09:35 PM
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Originally Posted by xvfx View Post
I'm surprised most don't use CIE2000.
dE76 is the most ruthless tool for greyscale. ... IMO, one should remove as much absolute mathematical error as possible regardless of so-called "perceptual" weighing.

CIE2000 is for when you want to "feel good" about the errors you can't fix.
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post #4202 of 4209 Old Yesterday, 10:30 PM
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Originally Posted by HDTVChallenged View Post
dE76 is the most ruthless tool for greyscale. ... IMO, one should remove as much absolute mathematical error as possible regardless of so-called "perceptual" weighing
There isn't a whole lot of difference between DE76, DE94 or CIE2000 near the neutral axis - most of the tweaks are in the saturated colors which tend to be de-weighted in DE94 and CIE2000.
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post #4203 of 4209 Old Today, 08:52 AM
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Originally Posted by gwgill View Post
There isn't a whole lot of difference between DE76, DE94 or CIE2000 near the neutral axis - most of the tweaks are in the saturated colors which tend to be de-weighted in DE94 and CIE2000.
All I'm saying is that little "errors" add up in a Y/Cr/Cb color system ... if your "zero" is really something like "0.1," that just makes it harder to find all the other colors. So be as ruthless as possible when you can.
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post #4204 of 4209 Old Today, 07:24 PM - Thread Starter
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HCFR - ArgyllCMS meter correction comparison

I wanted to compare the meter correction technique that HCFR uses (RGBW 4-color matrix solution) to what ArgyllCMS is doing to evaluate any differences. The data below was obtained via the following:

1. Profile a D3 against the JETI-1211 using ArgyllCMS
2. Measure a test set with the JETI-1211 and the profiled D3
3. Profile a D3 against the JETI-1211 using HCFR
4. Measure the test set again with the HCFR profiled D3
5. Remeasure with the JETI-1211 for repeatability

In Step 1 ArgyllCMS calculates the best-fit matrix that minimizes color difference errors between the two probes (as opposed to the closed form solution of the 4-color matrix method). For this method I used a profiling set of 22 colors consisting of 25% increments along each color axis and ~11% increments along the neutral axis.

Steps 2-5 use a different set of 37 test colors at higher density along each RGBW axis.

Steps 3 and 4 were repeated using both 100% RGBW and 75% RGBW patches to form the HCFR correction matrix.

Results show that the ArgyllCMS method reproduces the reference values somewhat better than the 4-color method and the 75% level-based a tad better than the 100%, although the absolute color differences are pretty small (mean dE2000: best-fit =0.19, 75% 4-color=0.26, and 100% 4-color=0.39). Repeatability was excellent at 0.09 dE2000 mean difference.

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post #4205 of 4209 Old Today, 08:58 PM
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Can someone please explain why do we need a spectrophotometer along with a colorimiter?
Are the results a lot better when using a correction matrix?

I've been calibrating my displays with i1D2 then with i1D3 for years, was is "not accurate"?
Is a difference of 0.5 THAT visible?
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post #4206 of 4209 Old Today, 09:05 PM
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Originally Posted by zoyd View Post
Results show that the ArgyllCMS method reproduces the reference values somewhat better than the 4-color method and the 75% level-based a tad better than the 100%, although the absolute color differences are pretty small (mean dE2000: best-fit =0.19, 75% 4-color=0.26, and 100% 4-color=0.39). Repeatability was excellent at 0.09 dE2000 mean difference.
That's pretty interesting, since I haven't done such a comparison myself.

Any feeling whether Argyll's fitting makes any difference (better or worse) when just using 4 patches (RGBW) ?
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post #4207 of 4209 Old Today, 09:06 PM
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Originally Posted by James Freeman View Post
Can someone please explain why do we need a spectrophotometer along with a colorimiter?
Are the results a lot better when using a correction matrix?
The point is to use the Spectrometer to create the correction matrix.
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post #4208 of 4209 Old Today, 09:09 PM
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Quote:
Originally Posted by James Freeman View Post
Is a difference of 0.5 THAT visible?
if I understand correctly, the 0.5 is the difference between the i1d3 and jeti after profiling, not before.
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post #4209 of 4209 Old Today, 09:22 PM
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Originally Posted by gwgill View Post
The point is to use the Spectrometer to create the correction matrix.
I understand, Thanks.
Will a spectrometer improve the calibration of the Greyscale or only the Colors?

From what I've seen I think that a well behaved Greyscale and Gamma are much more important than sub 3dE color errors.


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