[argyllcms] Re: Total Ink Limit (aka TAC)
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sat, 30 Dec 2006 16:32:54 +1100
Martin Weberg wrote:
profile -v -qm -kp 0 .17 .9 1 .53 -l350 -L100 -SAdobeRGB1998.icc -cmt -dpp
FOGRA39L.ti3
Quick calc -> 87+77+60+100=324%?
(icclu ... -ip ... -> 322%)
Shouldn't it be more close to 350% if -l350 specified?
A few things:
The total ink limit is a maximum, not a target.
The ink limit is imposed at the grid vertices, and the
linear interpolation within grid cells and output curve lookups
may give outputs that sum over the limit.
The behavior of a CMYK device near black is not usually simple. In general
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 behavior
near black (ie., often adding yellow makes things lighter for some
pigmented inks).
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. Your result doesn't seem
unreasonable.
Graeme Gill.
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