[argyllcms] Re: Black point gamut

  • From: Martin Weberg <martin.weberg@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sat, 19 Sep 2009 16:05:02 +0200

Hi Klaus!

2009/9/19 Klaus Kompatscher <kkompatscher@xxxxxxxx>:
> I get a black point of approx L41 a 17 b 37.
> K black is L23 a 3 b 2.

I did make a profile from your data:
colprof -v -kp 0 .15 .9 .9 .5 -L100 SapphireGloss
[...]
Find black point
K only value (Lab) = 24.004226 0.869899 -1.800685
Black point XYZ = 0.158615 0.163662 0.138984, Lab = 47.451325 0.468539 -1.064285
[...]
This output is similar to your findings.

Then I tried sending Lab 0 0 0 abs col through SapphireGloss.icm:
icclu -fb -ia SapphireGloss.icm
0 0 0
0.000000 0.000000 0.000000 [Lab] -> Lut -> 0.997033 0.077146 0.008354
1.000000 [CMYK]
and back again:
icclu -ff -ia SapphireGloss.icm
0.997033 0.077146 0.008354 1.000000
0.997033 0.077146 0.008354 1.000000 [CMYK] -> Lut -> 18.511783
-1.502135 1.800392 [Lab]

And we end up with Lab 19 -2 2 which seem resonable.

Martin Weberg

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