Re: Digital Negs - RGB vs CMYK

From: Katharine Thayer ^lt;[email protected]>
Date: 12/04/04-02:16:30 PM Z
Message-id: <>


Jim Morris wrote:
> This is most likely caused by making CMYK separations based on SWOP
> inks. Equal amounts of C+M+Y theoretically should equal neutral, but
> this is not the case with SWOP inks. Because of certain impurities in
> the ink colors C+M+Y equals a reddish, muddy looking color. To make up
> for this, the C+Y+M combination requires more C to neutralize the red
> cast, and K to achieve a true black. If you look at the custom CMYK
> set-up window in Photoshop 7 you will see a little graph with curves
> showing how the colors are weighted for the separations. So, if you
> are using CMY pigments, say for gum printing, that actually produces
> neutral gray in equal amounts, then separations that are made based on
> SWOP inks will most certainly produce a cyan cast when printed with the
> gum pigments.
> Photoshop will do almost anything you ask it to do but it gives you a
> lot of options, the trick is to know what to ask. If you ask for
> separations based on SWOP inks, that's what you get. CMYK offers a lot
> of flexibility, and no, I'm not saying that it's better or worse than
> RGB. What I am saying is that CMYK has to be applied correctly in
> order to work the way you want it to and this makes it, seemingly, more
> complex. The notion of creating CMYK separations by default in
> Photoshop, throwing away the K, and printing in CMY, is almost as bad
> as making RGB separations and throwing away the B.
> I know that the default approach to CMYK is often recommended by people
> who should know better; it's just plain wrong.
> Jim Morris
> Joe Smigiel wrote:
> >> I certainly think you can get realistic/believable color
> >> with either RGB or CMYK separations, but accuracy is another matter.
> >> Most realistic-color gum images I've seen (primarily on the web) I
> >> would
> >> not call accurate. Many tend to have a cyan/blue bias IMO.
> >>
Received on Sat Dec 4 22:12:44 2004

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