RE: Prtg CMYK Separation NEGS in GUM

I'm not sure - refer to Don's post for a definition.

To see the difference in practice try this (in PS 6 and after):

1) Open an RGB file in Photoshop.
2) In PREFERENCES/COLOR SETTINGS, change the CMYK setting to UCR
3) Change the mode of your RGB file to CMYK
4) In the CHANNELS palette, take a good hard look at those channels.
5) Convert back to RGB
6) Now go back to COLOR SETTINGS and change the CMYK setting to GCR with
black generation = "medium". and the ink settings to 100 and 400, UCA to 0.
7) Convert to CMYK
8) Repeat step 4 and note the differences between these channels and the
ones in the prior CMYK space.

Keith

-----Original Message-----
From: Temi [mailto:Temi@TemiOriginals.com]
Sent: Monday, September 13, 2004 10:47 PM
To: alt-photo-process-l@sask.usask.ca
Subject: RE: Prtg CMYK Separation NEGS in GUM

" UCR and GCR " - WHAT DO THESE MEAN ? ? ? ?
Thanks, Temi

-----Original Message-----
From: Keith Gerling [mailto:Keith@gumphoto.com]
Sent: Tuesday, September 14, 2004 3:07 PM
To: alt-photo-process-l@sask.usask.ca
Subject: RE: Prtg CMYK Separation NEGS in GUM

"Really what it matters is black to be the last and never yellow as the
last
printing pigment."

Not really. It is a matter of pigments and of preference. When using
UCR
or GCR generated CMYK negs, I often like to put the black on first. I
like
to establish the shadows, and then continue to build the print with
layers
of color. Black pigment is so obvious, and it's presence on top can
sometimes he rather overbearing.

Again, it might be a helpful to mention that there is a world of
difference
between UCR and GCR-derived CMYK negs. Depending upon the method
chosen,
the amount of the yellow laid down is dramatically different. With GCR,
the
intent is to lest the color channels "build" the shadow density, thus
there
will likely be yellow everywhere, thus there will likely be an ugly
yellow
veil if one is using Cadmium or ochre. But with UCR the color is added
on
an "as-needed" basis - thus yellow only is put down where it is needed.

Here are examples of a gum photo where black was laid down first, and
yellow
last:

http://www.gumphoto.com/bowl.jpg
http://www.gumphoto.com/tree.jpg

That Tree picture is loaded with yellow, but notice that it doesn't
clobber
the black. The Bowl picture is more "normal" and I think these
illustrate
why one cannot issue any hard and fast rules regarding the order of
colors.
(Incidentally, for that tree shot, I used raw umber for the "C"
channel.)

Keith

-----Original Message-----
From: gdimase@hotmail.com [mailto:gdimase@hotmail.com]
Sent: Sunday, September 12, 2004 8:53 PM
To: alt-photo-process-l@sask.usask.ca
Subject: Re: Prtg CMYK Separation NEGS in GUM

I have heard that the printing order is yellow, magenta, cyan and black
but
printing yellow first is not easy with the white paper and you better do
magenta first, yellow after then cyan and black.
Really what it matters is black to be the last and never yellow as the
last
printing pigment.
Giovanni
>
Received on Tue Sep 14 08:04:56 2004