[argyllcms] Re: Black point gamut

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sun, 20 Sep 2009 16:53:25 +1000

Klaus Kompatscher wrote:
I got a strange situation with colprof.
When creating a profile with the attached ti3 file
I get a black point of approx L41 a 17 b 37.
K black is L23 a 3 b 2.
I can't find any patch L41 a 17  b37 (or close to it) on the test chart.
Whats wrong?

        the device response is a little strange, as there seems to be
negligible cyan. The strange gamut has then tricked the black point
finding code into settling on a local rather than global minimum.

I will tweak the code to try and avoid such a situation, but the device
response is something you will have to attend to :-)

A truer black point would be Lab = 24.219132 1.033186 -1.430985.
Note that the black point doesn't correspond to any particular patch,
it is the darkest black within gamut in the direction of K only.


Graeme Gill.

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