[argyllcms] Re: CMYK Profile Problem
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Tue, 16 Mar 2010 02:32:56 +1100
Idea Digital Imaging wrote:
Interesting. And the black in this profile is warm...
Yes, this explains what you are seeing.
So, working as designed, but feel free to convince me that this isn't
the right
way to choose the black point for a CMYK device !
I can only convince you that a full black of C57 M67 Y72 K100 is a PITA
to work with :(
My theory was that usually black ink has a very flat absorption spectrum,
so that typically the K only hue is a good match to the plain paper.
The fact that typically press control matches CMY to K only,
and that a high K image has better neutrality under different illuminants
supported the notion that this was a good idea.
[Doing tricks with crossing over from K only to rich black also
work better when the black points are in the same direction.]
If the K ink isn't very flat, then maybe it's not such a good basis
to pick the black point ?
For a press, wouldn't it be better to work with a theoretical black
point which is the black max + neutral CMY ratio = total ink limit ?
That's generally the case, but there's no guarantee that the deepest
black is on the total ink limit boundary. (If yellow was quite reflective
for instance, it might decrease density after some point).
My assumption was that using -S would generate a perceptual table that
behaves in the same way a device link with perceptual intent and gamut
mapping from sRGB to PSO_LWC_Improved would.
It should, yes. It's not quite as smooth or accurate, but the transform
aims are the same.
This would create a profile that can be used in Photoshop in the same
way that I use the profiles I've previously adapted using Profilemaker
-- only with a better, gamut mapped perceptual conversion.
Yes.
Graeme Gill.
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