[argyllcms] Re: Displays with internal gamut emulation

  • From: János, Tóth F. <janos666@xxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 18 Aug 2010 16:08:28 +0200

>  In the graphs you show, what is the horizontal axis - time ?
>

No, that is the luminance. :)
I measured every steps on red, green, blue and white gradients [0..255]. The
gamut emulation is not perfect on the near-black shades, and this will
produce colorized grays after the VGA LUT calibration.

You can't notice the slightly over saturated colors on dark shades but the
software will miss the white balance because it assumes stable primary color
saturations (I think).

Sounds like the best solution. Leave the primaries native, and adjust
>  the transfer curves to have the sort of gamma you want.
>

Ja, ja. You don't have to say me this. The problem is that I can't access
the internal LUTs.
It was a poetical question, if somebody may know how to do it... Dell
doesn't offer any automated calibration softwares (like the EIZO
ColorNavigator)  or service tools (to readjust the strange factory
settings).

I lose a lot of contrast ratio when I try to calibrate the usable native
gamut modes. But I am "working" on a solution for this: I want to set the
white balance with the RGB Gains (the RGB Level graphs are nice and stable
in this display mode) and do a VGA LUT calibration with "native white" and
desired gamma (2.2) curve targets.
It won't be "perfect" because the VGA LUT works with effective 10 bit/color
precision while I can set the Gains with 8 bit precision in the service OSD.
This won't work in the emulated modes where the RGB Level graphs are
crossing each other.

By the way, I want to use the sRGB emulation display mode for PC games where
there is no way to do a software based gamut correction. And the display
does it with 12 bit internal controller while softwares do it with the 8 bit
framebuffers.
(I have a gamma remap bypass tool to keep the VGA LUT loaded under D3D
FullScreen programs.)

 I'm not sure why you are focussing on the primaries. If they aren't
>  stable, won't every other measurement be unstable too ?
>

I am not sure about the solution.

 There will be another important bug fix in V1.2.2
>

Yes, I only read about the fix and I assumed you corrected the problems.
I still have some "Misread, Retrying..." messages.
Will it affect the calibration precision? Are the current measures correct
after the software gets over this hangups?
Is there an ETA?

Some other examples - These are the calibration curves with unadjusted
(maxed 255) RGB Gains:
Standard mode: http://img12.tar.hu/janos666/img/82927235.png
sRGB mode: http://img12.tar.hu/janos666/img/82927234.png
Yes, the Standar mode starts with a little out-of-box banding issues (but it
has the highest contrast ratio to start with).
(The black offset was 100% and the black level correction was 0%, with a
rate of 400 - In DispcalGUI 0.5.1)

Other related posts:

  1. Home
  2. argyllcms
  3. Archive
  4. 08-2010