RE: Prtg CMYK Separation NEGS in GUM

From: Keith Gerling ^lt;[email protected]>
Date: 09/14/04-07:18:35 PM Z
Message-id: <>

CMYK is a device that was created in order to let designers and graphic
artists communicate with commercial printers. CMYK is not a universal sort
of "standard" like RGB, but rather method of setting up an infinite number
of possible ink settings, and conveying these settings to the person running
the printing press. The different settings allow for differing means of
balancing cost against quality. As black ink is usually cheaper, the GCR
method emphasizes using as much black as possible to get an acceptable
result, and only uses color where it is needed. UCR assumes that shadow
densities will be built up using all of the colors. UCR gives "normal"
looking negatives, allows the user to set the black amount AND depends on
the building up of layers of ink (gum) to affect the DMAX. With UCR, the
dark areas get major doses of all color ink/gum and if you print only one
channel, it will still look pretty "normal". GCR C, M, and Y negs can look
a little strange, as the shadow areas (which rely upon the black channel)
are very thin.

In practice, I often switch back and forth from GCR to UCR - perhaps using
the M and K channels from a UCR derivation and the C and Y from GCR. All of
this might sound complicated, but its pretty easy to understand after
playing around with Photoshop settings for 10 minutes.

Oh, it occurs to me while writing this that I had UCR and GCR switched
around in my previous message. Those two gum prints used the GCR method.


-----Original Message-----
From: []
Sent: Monday, September 13, 2004 1:09 PM
Subject: Re: Prtg CMYK Separation NEGS in GUM

It's not clear to me.
Could you tell me what GCR and UCR stand for in digital negative terms?
Let's make it easier saying Photoshop terms.

----- Original Message -----
To: <>
Sent: Tuesday, September 14, 2004 4:06 PM
Subject: RE: Prtg CMYK Separation NEGS in GUM

> "Really what it matters is black to be the last and never yellow as the
> 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
> 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
> between UCR and GCR-derived CMYK negs. Depending upon the method chosen,
> the amount of the yellow laid down is dramatically different. With GCR,
> intent is to lest the color channels "build" the shadow density, thus
> 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
> last:
> That Tree picture is loaded with yellow, but notice that it doesn't
> 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
> (Incidentally, for that tree shot, I used raw umber for the "C" channel.)
> Keith
> -----Original Message-----
> Sent: Sunday, September 12, 2004 8:53 PM
> To:
> Subject: Re: Prtg CMYK Separation NEGS in GUM
> I have heard that the printing order is yellow, magenta, cyan and black
> 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
> printing pigment.
> Giovanni
> >
Received on Mon Sep 13 17:21:42 2004

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