CMYK to Lab bug plug_1
CMYK to Lab bug plug_1
- Subject: CMYK to Lab bug plug_1
- From: Henrik Holmegaard <email@hidden>
- Date: Sun, 8 Apr 2001 18:49:45 +0200
Round about three years ago Jim King took the stand at Seybold and
said CIEBased predated ICC, CIEBased was smart, CIEBased was
neglegted, so CIEBased would be revived.
Round about two years ago the Pshop folks posted here on the List
that being against CIEBased was being against device independent
color management to which the reply this side was that real world
device independent color meant ICC. And I guess both sides would have
agreed that those who want to run device colors could run device
colors. That was the original Level 1 idea. If you know your party's
extension number, just dial direct, so to speak.
Currently, CIEBased is in trouble because it breaks the workflow. I
take it the other side of the pond can agree so far.
PDF 1.2 and PDF 1.3 (and PDF 1.4, I'll chance) don't support calCMYK,
so a CMYK object that references a CIEBasedDEFG Color Space Array
gets converted into Lab, even when you select 'Leave Colors
Unchanged'.
Whether Photoshop 5.0, 5.02, 5.5 and 6.0 embed a CMYK CSA into a CMYK
EPS, or the CMYK CSA is embedded into the CMYK object using the
PostScript Color Management option in the Illustrator, Photoshop (and
InDesign though I'd have to test that, come to think of it) print
dialog, the result is the same: The CMYK object is turned into Lab as
a simulation.
The rule in late binding, scan once output many workflows is that you
use Lab or ICC tagged RGB for high gamut digital originals. You don't
create Lab simulations for circulation among innocent bystanders.
The logic of this is that if you want to do a CMYK to CMYK
conversion, you apply the same intent on both sides of the connection
space. You don't have one intent on one side and another on the other.
Therefore, if you do a CMYK to Lab conversion, the downstream
workflow doesn't know what conversion to apply next. There is no
trace of the first half of the conversion left to go by. I mean,
short of visually inspecting every Lab object in every page of every
PDF file.
This is a bug the size of a barn. You can drive a truck through it.
You can also stack hay in there, come the month of May -:).
(End of part 1)
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Henrik Holmegaard, TechWrite
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