[argyllcms] Re: Display profiling problem

  • From: George Pop <gapop@xxxxxxxxxxx>
  • To: <argyllcms@xxxxxxxxxxxxx>
  • Date: Wed, 28 Mar 2012 15:39:43 +0300

I finally managed to create a profile that solves my black crush problem. The 
solution was to select the "gamma + matrix" type. Could someone please explain 
why I had success with this, but not with shaper/matrix or LUT + gamut mapping?

Does using a gamma + matrix profile make the "perceptual" option in color 
managed apps meaningless?

Is the fact that matrix-based profiles cannot have the Perceptual intent a 
limitation of Argyll? Inspecting with iccdump some profiles created with other 
software, they look more like matrix profiles (no A2B tables), and yet in the 
header they indicate Perceptual as the rendering intent.



From: gapop@xxxxxxxxxxx
To: argyllcms@xxxxxxxxxxxxx
Subject: [argyllcms] Display profiling problem
Date: Sun, 25 Mar 2012 02:34:31 +0200


I am in over my head trying to solve a display profiling issue. I hope that 
someone more knowledgeable on this mailing list will help me.

I have a monitor (Samsung F2380) with a black crush problem that is not subtle. 
A lot of details in the shadows in photos and video are lost.

For a while I've used this monitor with a profile that I found on the Web. That 
profile has worked wonders, completely solving the black crush problem. Photos 
with a full tonal range can now be displayed with excellent contrast and no 
loss of details. But it has a color cast which I wasn't able to fix using the 
RGB settings in the monitor's menu.

So recently I bought a colorimeter (the Colormunki Create/i1Display2) and have 
used it with dispcalGUI and Argyll 1.3.6. The resulting profiles get rid of the 
color cast, the grays are spot-on. But the black crush problem is back.

I have tried both "Curves + matrix" profiles and "XYZ LUT + swapped matrix". On 
the latter, I activated gamut mapping for perceptual intent (using sRGB from 
Argyll as a source profile) and have successively tried "Luminance matched 
appearance", "Perceptual", and "Perceptual appearance" as gamut mapping 
intents. The "default intent for display device profile" is Perceptual, and I 
also made sure that my color managed apps use perceptual. The differences 
between these profiles are marginal as far as the black crush problem is 

My calibration and profile settings are: D65 white point, native white level, 
native black level, gamma 2.2, high quality calibration & profile, BPC on. I've 
also tried native white point, gamma 2.4 (worse), 2.0 (also worse) and L* (this 
did open the blacks a little, but the midtones and highlights are too high).

I don't know what else to try. I've been brute forcing the calibration settings 
with considerable waste of time and constant disappointment.

Can any information be recovered from the profile I found on the Web to figure 
out what makes it work so well for tonal range?

Any suggestions would be welcome.





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