RE: RGB vs CMYK: gamut and some important notes for CMYK users

From: Keith Gerling ^lt;[email protected]>
Date: 12/04/04-11:29:25 PM Z
Message-id: <>

Sorry, you lost me. If "out of gamut" is not an issue for separation
negatives, then when is it an issue? A "gum color space"? I have been
reminded that for the purposes of this discussion CMYK equals "the CMYK
settings that arrive with Photoshop" Curves and image adjustments do not
define color space, they adjust the image in whatever color space has been
chosen. I'm with you on that last sentence, but what is the printer/inkset
color space, if it is not the CMYK settings?

Upon reading this entire thread, some people might come to the conclusion
that CMYK is inferior to RGB. This, because it alters the data carried in
the RGB file and thus looks less true on a video monitor. This data is
changed intentionally during the CMYK conversion, and it is changed in order
that the closest colors possible to the original photograph are in the
output. Taking into account the parameters specified in the CMYK setup, and
the specifications of the ink that is chosen, the CMYK channels look
different. Those inksets in CMYK are important.

 -----Original Message-----
From: []
Sent: Saturday, December 04, 2004 11:44 AM
Subject: Re: RGB vs CMYK: gamut and some important notes for CMYK users


  I don't think that "Out of Gamut" would necessarily apply in the case of
making seperation negatives, since instead of using the printer/inkset color
space, you are using the "Gum Color" space you have chosen. The curves you
use for full color gum and the color pigments are what will determine the
look of the final image.

  Mark Nelson
  Purchase the book @
  Credit Card & Paypal now accepted

  In a message dated 12/4/04 12:16:51 PM, writes:

    Has anybody brought up the issue of "out of gamut"? Reflecting upon the
    examples provided here, I remembered that I had read that Adobe (and the
    revered Blatner and Fraser) have always recommended that RGB should
never be
    used for anything but video monitor output. Digital printers, film
    recorders, and printing inks cannot reproduce the entire RGB spectrum.
    Photoshop's "separation engine" makes every effort to fill in
    pixels with the closest colors available given the specified ink and
    separation settings. Output in RGB will result in "gamut-clipping":
    in the image that contain will contain no information in a non-video
    output. (However, this may be a non-issue. If, as it was pointed out,
    printers automatically convert to CMYK, are those gaps filled in? I
    know, because I don't output to a printer.)
Received on Sat Dec 4 21:28:18 2004

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