[argyllcms] Re: B2A mapping of out-of-gamut colors
- From: Klaus Karcher <lists@xxxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Wed, 02 Jan 2008 12:08:10 +0100
Thomas Baumann wrote:
Hello list,
when I print a Lab test target through any of my Argyll generated
printer profiles there is a peculiarity, most pronounced with
relative colorimetric intent: Dark out-of-gamut colors with high b
values turn into a light yellow - see file
Screenshot_Softproof_Argyll.tif.
Example (B2A1, L = 9, a = 0, b = 80):
So the problem seems to lie in the gamut mapping [...] from a very
dark to a very light yellow.
The problem is that Lab 9/0/80 is not a "very dark yellow" but no color
at all. When you take a look at e.g.
<http://brucelindbloom.com/LabGamutDisplay.html>, you will find that
9/0/80 is far beyond the gamut of the human vision.
I don't know exactly how argyll deals with "virtual" colors like this
(I'm sure Graeme can explain it in detail), but a yellow with a much
higher L value seems to be a reasonable substitution for this "un-color".
Klaus
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