jmorris@morriseditions.com
Date: 09/08/02-12:35:45 PM Z
----- Original Message -----
From: Katharine Thayer <kthayer@pacifier.com>
To: <alt-photo-process-l@skyway.usask.ca>
Sent: Sunday, September 08, 2002 4:30 AM
Subject: Re: CMYK Gum Prints and Color Gamut
> At the time, I argued that since the
> Photoshop CMYK space was developed to optimize commercial printing
> processes-- commercial inks, commercial paper, commercial printing
> presses--it didn't make sense to me to assume it was the best CMYK
> space for the gum process, and I said, half in jest, that someone should
> develop an ICC profile for gum. I got the feeling that no one had a clue
> what I was talking about. (When I printed color I worked in tricolor not
> CMYK so I had no interest in developing such a profile myself.)
>
> Since then, of course, the level of knowledge about photoshop and
> digital printing of negatives has increased around here exponentially,
> and several people have worked on curves for gum, but I haven't heard
> that any of them has developed a CMYK profile for color separations for
> gum. If I'm wrong, I'll be happy to be corrected.
Before color management was incorporated into Photoshop (prior to version
5.0) it was probably true that, in a practical sense, the default CMYK was
geared more to offset printing than anything else. Since version 5.0,
however, the ability of Photoshop to use ICC profiles has opened the door to
predictable input and output in any number of color spaces. This
predictability, however, is predicated on a fixed set of factors. That is to
say that the ICC profile is, generally, a description of input and output
behavior from a device in a known and repeatable state, for specific
materials under, more or less, specific conditions (that's a mouthful). This
is why profiling a device like a digital camera becomes problematic, as
lighting alone becomes an infinite variable. So... you can imagine the
number of variables gum printing might introduce. While it would certainly
be possible to profile specific gum printing procedures, the separations
that would result would only be good (depending on how critical you are) for
those specific procedures and materials; all bets would be off the moment
the procedures or materials changed.
That being said, I think the idea of profiling CMY or CMYK gum printing is
cool. Another thing you could do is create tables in Photoshop of various
pigments for duotone, tritone and quadtone gum printing. However, I think
the starting point for success (more or less) using ICC profiles or
Photoshop tables would be a rigid standardization of printing procedures and
materials (which might take some of the fun out of gum printing).
Jim Morris
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