Re: CMYK separations on Adobe Photoshop

From: Joe Smigiel ^lt;>
Date: 11/03/04-01:41:39 PM Z
Message-id: <>

>>> 11/03/04 4:25 AM >>>
Keith, I got into this discussion when Joe said that only the CMYK file
contains correct color information and that color separations from the
RGB file will give a distorted color balance in a tricolor print, and
advised that people should always convert to CMYK before printing
separations. This is not consistent with my own experience, and I said
so. I suspect Joe still doesn't believe that I can print true color
(when I want to) from RGB separations, and I haven't found a way to
prove it for him, so that's just going to have to remain unresolved. <<<

Not quite. I said in regard to the RGB set: "Be aware that this set of
negatives will be distorted in terms of color printing characteristics
compared to those made using the CMYK mode and selecting those
individual channels for negatives. The info preserved just isn't the
same, but can be interesting nontheless."

My statement never puts forth any absolute about which set is better.
Nor did I ever say that people "should always convert to CMYK before
printing separations" as you've implied. Rather, I stated a general
conclusion regarding results of one set relative ("compared") to the
other based on my experience. The results of my recent test strengthens
that observation and, at least with the image I'm printing now, confirms
that my set of CMYK negatives made a more accurate transcription when
everything else was held constant. In a later post I did say I believed
CMYK negatives gave more "accurate" transcriptions. Having not seen any
visual evidence to the contrary (i.e., another side by side test of a
RGB vs. CMYK set of negatives printed in gum) I still hold that belief.

I also never said that you personally would not be able to print "tue
color" when you wanted to from the RGB set.

Please stop making such unfounded projections and inferences regarding
what I believe or say.

I've never claimed to be any expert on this topic and was simply
relating my experience and what I've read about separations. I offered
the RGB method as an alternative and did so with a friendly intent and
attitude in contrast to the critical tone you came back with.

What I objected to in your reply was:
"...and since I know of
several other gum printers who also work directly from the RGB file and
also get beautiful and true colors, to my mind the general conclusion
Joe seems to be drawing, that if you print from RGB files you will get
weird and distorted colors, is problematic because there is so much
available evidence to the contrary."

I politely asked for an example of who these "several other gum
printers" are "with so much available evidence to the contrary." You
have failed to produce even one example though I've asked twice now.
And, not that a single test would provide any real resolution to the
question, but apparently you have two sets of personal negatives to
compare results yet you state that won't print the CMYK set. Doing so
would at least add some additional concrete visual information to the

A check of the archives will reveal that gum workers contributing to
this list get widely varying results using the same materials and that
the method and materials that work for one person don't necessarily work
for another. Personally, I don't have very good results with W&N Winsor
Blue which is a staining phthalocyanine pigment in my experience, and I
don't believe Paul Andersen's gum-pigment ratio test is valid as stated
in many texts and which is a belief held by several gum printers on this
list. I've done the test by the book several times and have always
arrived at that same conclusion. Others apparently have different
experiences, results, and beliefs. Fine. No problem. I'm just
relating my personal experience. YMMV. But, I'm also not taking things
out of context, making inferences, misquoting other posters, and
refusing to show my results hoping that some pronouncement I make will
suffice to convince others.

Leave me out of your posts in the future.

Sorry to bother the list with this.

Received on Wed Nov 3 13:40:41 2004

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