[argyllcms] Re: Using a Sequel Chroma 4

  • From: "Preben Soeberg" <prsodk@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 7 Dec 2007 11:46:20 +0700

I guessed the chroma 4 is much like the Eye One Display as it was
originally a OEM variant of the Chroma 4.

So, in i1disp.c, I changed the code to look like this

At the top of the file
static boolean chroma4 = FALSE;

At line 1100:
if (ver < 5.1) {
   vv = 'L';
   chroma4 = TRUE;
}
if (ver >= 5.0 && ver <= 5.3 && vv == 'L') {

At line 1300:
/* RGB channel scale factors */
for (i = 0; i < 3; i++) {
   double tt;
   tt = (double)p->reg44_S[i] * 1e11/((double)p->reg40_S * (double)p->reg42_S);
   if (chroma4) tt *= 4;          //  Multiply white level reading with 4 to
be more correct

The last hack was made to give white level around 140 Cd/m^2 using
dispcal -yl -r.
This also gives correct reading for maximum brightness according to
monitor specifications.

It works like a dream, though I cannot rely on the absolute value of gamma.
Setting -g1.75 in dispcal gives a final gamma of 2.2 (according to my
gamma swatches, downloaded from Timo Autiokari).
I'm leaving Nvidias settings from installation time untouched.

I do not understand the black point setting, as I see it in the
calibration file:
BEGIN_DATA
0.0000 0.019102 0.018301 0.017533
3.9216e-003 0.025279 0.024478 0.024011
7.8431e-003 0.031338 0.030534 0.030370

I don't understand why is it not going down to more near zero.

> Preben Soeberg
>

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