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

  • From: David Heinrich <dh003i@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 9 Dec 2009 23:16:36 -0500

I'm having problems hitting the desired white-point / color temperature via
adjusting RGB gain while maintaining my desired brightness. I want a
brightness -b of 96, and specify both -T and -t as 6500.

I'm using a Sony GDM-F520 CRT monitor. There are three basic "modes" for the
monitor: Professional, Standard, and Dynamic. If I put it in Professional
mode, I can't hit the 6500 white-point while maintaining a brightness of 96
cd/m^2. I can hit it in Dynamic mode very approximately hit the white point
while keeping a brightness of 96 cd/m^2.


sudo ./dispcal -v -d2 -yc -ql -b96 -gs -H -t 6500 -T 6500 -e4 -P0.5,0.5,3 -o
gdmf520-shaper-matrix

2) White point (Color temperature, R,G,B, Gain/Contrast)
\ Current Br 99.96, x 0.3125, y 0.3235  DE  0.8  R++ G-  B+
/ Current Br 100.02, x 0.3126, y 0.3243  DE  1.3  R+  G-- B+
\ Current Br 99.97, x 0.3129, y 0.3244  DE  1.1  R+  G-- B+
/ Current Br 99.71, x 0.3127, y 0.3229  DE  0.4  R+  G+  B--
/ Current Br 99.40, x 0.3134, y 0.3222  DE  1.1  R-  G+  B--
/ Current Br 100.03, x 0.3126, y 0.3245  DE  1.4  R+  G-- B+

Those are some examples of readings I get when I put the CRT in Dynamic mode
and adjust he brightness / black level (1) first, then the white point via
altering RGB gain/contrast controls on my CRT.

Why are the readings bouncing around? Troy Sobotka tells me he gets dE of
0.2 on a TN panel LCD he uses and that the readings are stable. So what's
wrong here? Either I'm doing something wrong, or something's wrong with my
CRT (it looks fine), or something is wrong with the Spyder2 colorimeter I'm
using.

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