Re: Profile Editing Software!??
Re: Profile Editing Software!??
- Subject: Re: Profile Editing Software!??
- From: joel <email@hidden>
- Date: Wed, 25 Sep 2002 17:39:40 -0500
on 9/24/02 11:19 PM, Reve at email@hidden wrote:
The problem is some of the color cannot be reproduced
on a printer like "blue turns purple" and the color is very
dull especially red color. I know that this is due to the small
> color gamut.
Most profiling packages have formulas which map RGBCMY to the
destination ink channels; what I refer to as gamut mapping from the
software's default source Lab to destination Lab as represented in
ink channel mixes.
Many default to process (SWOP?) ink conversions which overcompensate
one ink over another in their RGB-to-CMY conversions:
R=M+Y (often too much yellow)
G=C+Y (often equal measures of cyan and yellow)
B=C+M (often too much magenta - because the cyan channel is usually
heavy to start it is automatically limited by either the application
or the ink limiting process.)
Add GCR and 'secret sauce' considerations, plus added inks like Or,
Gr, Lc, and Lm to the equation and you can wind up with tainted
resultant color mixes as well. Preview tags often cannot accurately
replicate the results in applications which are centred on RGB and
CMYK representations.
R=M+Lm+Y (no documentation on the ratios of M to Lm)
G=C+Lc+Y (same - no doc)
B=C+Lc+M+Lm (same - no doc)
CMYtoCMY appears relatively straight forward with the exception that
piezo print process software screening algorithms (and/or
applications and/or printer drivers) do not print single solid ink
colors when they are not absolutely identical to the printer
software's CMY tables. (I'm not even sure if they do when they do
with the exception that a device independent postscript file from
InDesign 2.0 with embedded eps appears to print solid ink per
channel.) Hexachrome and hexachrome seperated DCS 2.0 files also
appear to address individual ink channels directly, though I haven't
done enough work to address this.
Add to this RGBtoCMY query: inkjet inks are different in comparison
to their SWOP and Sheetfed cousins. When building proofing profiles a
certain amount of tainting is required to 'simulate' a press inksets
differences.
Some profile building applications put gamut mapping RGBCMYtoLab (or
channel) up front at point of generating the profile. Others use
different gamut mapping tools, but usually up front at point of
generation. My experience has been you only have one, sometimes two,
kicks at altering gamut mapping before the profile itself is toast.
I have yet to see or demo a profile editor which addresses this issue
in a comprehensible manner worth the price of the editor.
Then again. I have yet to write on this topic in a comprehensible
enough manner to say I could do better than the existing software. ;0)
--
joel johnstone
Color Canuck
(It was in my head but I lost it in the ColorSink!)
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