Re: CMYK separations on Adobe Photoshop

Khatarine wrote:
If you're talking about the default Photoshop CMYK
> space, you are talking about a space that was designed to optimize the
> printing of color images in commercial printing inks on coated
> commercial printing papers; this space distorts the color information in
> the original file to accommodate the characteristics and limitations of
> printing inks and papers and has nothing whatever to do with printing
> pure pigments in gum on art paper.
 Following this interpretation of CYMK how do you "accomodate" pure pigments
in gum on art paper?
Yes, when you switch by Photoshop to CYMK and produce the 4 layers on
negative and print them the picture is not "accomodate".
Yes, we go back to the issue of GCR and UCR with endless possible
"accomodations" by changing the variables on color settings with black
generations and ink settings.
What is your experience on this matter and gum printing.
Thanks,
Giovanni

----- Original Message -----
Wrom: NNYCGPKYLEJGDGVCJVTLBXFGGMEPYOQKEDOTWFAOB
To: <alt-photo-process-l@sask.usask.ca>
Sent: Sunday, October 31, 2004 5:20 AM
Subject: Re: CMYK separations on Adobe Photoshop

> Joe Smigiel wrote:
> >
> > >>> gdimase@hotmail.com 10/29/04 11:48 PM >>>
> > Sorry, but...
> > How do you get the Cyan channel from a RGB file without going to CMYK?
> > Isn't this the question?
> > How do you get the Cyan colors?
> > Giovanni
> >
> > I'm just printing the RGB red channel negative using a cyan pigment (in
> > the image example, Linel Hortensia Blue). The green channel is printed
> > with magenta and the blue channel gets printed with yellow pigment. As
> > I've said and the image example shows, the colors are different in the
> > final image than when you do a CMYK conversion and make separation
> > negatives from those files. If you want a more accurate transcription
> > you should do the RGB to CMYK conversion.
>
> I'm sorry, I'm afraid I must disagree with this advice. It supposes
> that the CMYK file has accurate information in it and the RGB file is a
> distortion of that "accurate" information. This is backwards; the
> accurate information is in the RGB file; changing it to CMYK distorts
> that information to a greater or lesser extent depending on the CMYK
> space that's used. As Keith keeps pointing out, you can't talk about
> CMYK as if it were one thing, because there is an infinite number of
> possible CMYK spaces. If you're talking about the default Photoshop CMYK
> space, you are talking about a space that was designed to optimize the
> printing of color images in commercial printing inks on coated
> commercial printing papers; this space distorts the color information in
> the original file to accommodate the characteristics and limitations of
> printing inks and papers and has nothing whatever to do with printing
> pure pigments in gum on art paper.
>
> Joe's example is interesting but inexplicable to me. It seems to be
> offered in part to prove that RGB files print with weird, brownish
> distorted colors, but since I have always printed from the RGB file and
> have always got very nice, clear and true colors, 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.
> Katharine Thayer
>
Received on Sun Oct 31 21:29:13 2004