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

From: Judy Seigel ^lt;[email protected]>
Date: 12/05/04-10:09:12 PM Z
Message-id: <Pine.NEB.4.61.0412052218410.14452@panix1.panix.com>

On Sun, 5 Dec 2004, Keith Gerling wrote:

> Judy - No, I was not referring to paint OR to ink of a digital print, but
> rather to a specific required inkset parameter selection in the Photoshop
> color space setup. I said "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"

If I had the sense god gave leaf mold, I'd probably let this drop because
I am going to sound dumb -- but let us consider it a public service...
speaking for others who don't understand either, but are more discreet.

Keith -- WHAT ARE YOU TALKING ABOUT? Yes, it's poetry. For instance,

US Web Coated SWOP v2
Adobe (ACE)
perceptual
use black point compensation
use dither

Just add a faint rhyme... whither?

So you prove (as if we didn't know) that every decade (or sooner) one's
hard-earned skills become utterly obsolete. I learned color separation
manually for dye transfer, an agonizing process that required floating the
35 mm in oil, excruciating development of arcane materials, point light
source, keen analog eye, etc. etc. etc, taking an entire semester to
generate one set of matrices and one print... The EASY method for color
seps was tripack filters on the camera... (And then we split a few rails &
walked 30 miles barefoot through the snow.)

So when I did some color-separated gums by default settings (and they were
CMK, Chris, not RGB) they were blissfully simple, in fact so simple (that
was one of the reasons) I lost interest. Now, blessings on this list, you
make it seem hard again. But I ask only what seems within possible reach:

I did enter the Photoshop "colorspace" when generating those years ago
laser printer color seps -- usually printing from a CMYK setting, tho not
printing the K. The prints actually showed no real difference from negs
with black removed (CMY) and when I did make the K neg I never found a way
to use it in the print... BUT, that was Photoshop 3 or 4, which may have
been a blunter instrument. (Consider that an aside, not my question(s),
which are:)

***When you speak of the Photoshop "inksets" then, you don't mean actual
physical sets of actual physical inks, but theoretical combinations of (a)
monitor colors, and/or (b) printer ink colors that will be generated by
these specifications?

*** At the present time I have been making work prints (photos, not
negatives) on the 1160 -- using the settings in the 1160 printer
directory. I take it for those purposes there's no reason to dink around
with the Photoshop color settings.... or is there? If so, would 1160 care?

> ....If you were to go (in PS 7) into edit/color
> settings/working spaces CMYK, you will find a limited number of ink options.
> With a little trial and error, one can find a combination the suits ones
> purposes. Here is an interesting test: first make a duplication of your
> full-color RGB image. For one copy, change the CMYK inset to "Japan Color
> 2001 Coated". Convert mode to CMYK. For the other image, repeat the
> process using "US Web Uncoated v2", Convert to CMYK and toggle between your
> two images. Both CMYK, but pretty different, right? An experienced gum
> printer ought to be able to see how those two sets of separations might
> provide for different results when applied to gum printing.

Again, Keith, you're way ahead of me, but for starters, I take it you're
talking about "on the monitor" toggling. I won't torture you with more
questions (now), but can you make a general estimate of how closely
monitor image changes in such comparisons would (tend to) relate to print
changes in negatives made from each set of settings?

thanks, cheers,

Judy
Received on Sun Dec 5 22:09:29 2004

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