[argyllcms] Re: problems hitting white point (color temperature, RGB gain/contrast) while maintaining brightness: dE not stable

  • From: David Heinrich <dh003i@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 15 Dec 2009 14:04:21 -0500

On Fri, Dec 11, 2009 at 6:27 AM, Martin Weberg <martin.weberg@xxxxxxxxx>wrote:

> Return to factory defaults or similar.
> I usually don't move contrast settings.
> Then set brightness to something like 75% (or lower if your eyes are
> burning) to have some room to play.
> Then set all RGB channels to around 50%.
> If the display appears too bright lower the brightness. If too dim
> raise all RGB channels and maybe brightness. Be sure not to hit 100%
> or just below it.
>
> Now set the RGB channels to the desired white point using dispcal,
> ignore brightness. Then, try to match the brightness by altering the
> brightness control. If you are approaching 100% brightness pull back a
> bit and raise all R, G, B instead. Then, adjust white point again and
> brightness iteratively. If both brightness and one of the R, G, B
> channels are maxed you cannot meet your desired brightness target.
> Change target or display :-)
>

I followed Martin Weberg's suggestions. My readings still do not stabilize,
and are still bouncing around from a dE of 0.0 to even ~2 when adjusting RGB
gain channels.

I run the following:
sudo ./dispcal -v -d1 -yc -t6500 -T6500 -P0.5,0.5,2.5 -o sony-12-15-2009

So the issue is that I'm not getting stable readings for dE from target
color temperature. I've tried a variety of things; I switched from a BNC
connection to a VGA one, made sure my spyder2 was suctioned tightly on the
CRT, etc. What should I do from here? I presume if I go on to characterize,
the characterization will be hampered by these unstable values. Can I
characterize, or will it be worthless? (or maybe do several
characterizations and average them?).

I do remember from before it did say that when initially trying
characterization in several steps (using the dispcal output as a starting
point), colprof had "average errors of average errors of 5 or less, and
maximum errors of 15 or less" (this is what the colprof documentation
suggests is acceptable).

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