[argyllcms] Re: argyllcms Digest V3 #172

  • From: "Martin Weberg" <martin.weberg@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Sun, 31 Dec 2006 09:05:00 +0100

Graeme Gill wrote:

     The total ink limit is a maximum, not a target.

I'm with you.

    The behavior of a CMYK device near black is not usually simple. In
     there are multiple overlapping, discontinuous regions. For a given
target color
     (say L*a*b* = 0,0,0) it does not follow automatically that the
closest color
     will use the maximum possible ink. Some inksets have non-monotonic
     near black (ie., often adding yellow makes things lighter for some
pigmented inks).

Any suggestions on how to find the true TAC?

Having said that, I don't get quite the same results as you:

icclu -fb -ir FOGRA39L.icm
0 0 0 -> 1.000000 0.856338 0.575142 1.000000

with the sum 3.43148, but that's with my development code, which may
be a little different to the current release.

I can't get those numbers at all. Going from L*a*b* = 0,0,0 to CMYK (rel.col.)
I get:
0.874157 0.770432 0.600203 1.000000 (ArgyllCMS)
87 77 60 100 (Photoshop CS2, Adobe (ACE))
87.4189 77.0321 60.0153 99.9969 (LittleCMS, icctrans.dll for Matlab)

(you didn't do a new profile with the FOGRA39L-data with your development
code then running icclu?)

Martin Weberg

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