Re: Digital Negs - RGB vs CMYK

From: SteveS ^lt;[email protected]>
Date: 12/03/04-09:36:27 AM Z
Message-id: <002501c4d94d$db5e5c40$4804e4d8@VALUED65BAD02C>

This is a good thread, so I leave the components and add this from my

Using CMYK in photo light prints (enlarger with negs) I can subtract the
'layers' captured on film by dodging, but with computer aided technology, I
can separate them, and change their color. In other words. The capture of
details from the light wave in the form of negative density can be preserved
after separation and reprinted for clarity.

With RGB, these separations are harder to achieve, as the light waves'
impressions aren't detailed but mixed, which tends to confuse the image or
look muddled, without detail, blocked, fogged, burned out.

I find film gives a more detailed imprint to work with in the medium at the
start than electronic capture. Gum printing gives the artist a better
'potium' with greater range to render more exactly what they want to show in
their final picture. It comes back to what many have said in computer aided
photography versus the wet lab, you should have the experience of its
origins before taking on the advancements in photography.

The saying for printing color with an enlarger: "If the print looks red,
add red to the head." Makes sense all along the way to include alternative
processes. (except reversal films)

Steve Shapiro, Carmel, CA
----- Original Message -----
From: "Christina Z. Anderson" <>
To: <>
Sent: Friday, December 03, 2004 6:58 AM
Subject: Re: Digital Negs - RGB vs CMYK

> Hi all,
> How fun a thread; I have learned so much now!
> Thanks, Jim, for the post below, and thanks all others for their info,
> Jason DeFontes, that is the COOLEST website I have ever seen. What a
> wonderful setup you have done for the discussion! I am so impressed; you
> wanna design my website :)? I'm bookmarking it.
> Well, I am so glad I did not attempt a CMYK test before this most recent
> thread, because I would have assumed wrongly that each neg printed its
> opposite color. Here I was assuming a Livick typo...
> RGB makes logical sense to me, because I have a degree in photo and we had
> huge color processor in our darkroom. So this is how I learned
> photography--RGB. I admit it was a real stretch learning RGB color, since
> was doing my painting degree at the same time. Now I can't even think
> RYB is primary, I am so photographically accustomed. And, as I have said,
> color sep negs were done RGB, too.
> So I think the original question, posed by Joe S., was whether you could
> true color gums in CMYK as opposed to RGB. I do think the main
> characteristic with gum is its infinite adjustability: you start with
> whatever negs you have and adjust pigment, exposure, development to suit
> those negs. So you have at least (!) 3 variables to alter to determine
> final color outcome. There's not "one try" as in pt/pd or BW.
> That is assuming the color is put in the right place in the
> signs should be red, etc.
> It seems from Jason's website that if you let the other channels "absorb"
> (non-technical term) the black channel, it would work equally as well as
> RGB, given the gum variables. My guess is, that even if you didn't do
> 3 negs with the colors in their right places no matter what system should
> the job, when you adjust your gum variables to fit that system.
> Livick does perfect gum color with CMY, Sam does perfect gum color with
> Those are my benchmarks, I supposed, for both systems--the proof is in the
> pudding. It is doable either way, in gum if not in print or in color
> photography proper. I imagine that is why gum is so frustrating; we each
> develop our method that works, and can't understand why others don't use
> exact method because we are just soooo good.
> I alway remain open to learning from others. A case in point: in
> Experimental Photography I was on the Polaroid unit, and said you can't do
> image transfers with Time Zero. I also told students if they discover
> something new (after all, it was an experimental class!) I would add their
> discovery to my Exp. Ph. Workbook. I have a bunch of my students
> in there, and one, Missy Collins, now applying to grad school at the U of
> Minn, got transfers to work with time zero. In fact, her transfers will
> part of her application portfolio.
> Gotta love it when students prove you wrong.
> Chris
> ----- Original Message -----
> From: "Jim Morris" <>
> To: <>
> Sent: Friday, December 03, 2004 12:34 AM
> Subject: Re: Digital Negs - RGB vs CMYK
> > In CMYK the C prints C, The M prints M, etc. CMY is subtractive color
> > is used to create images that achieve color by light reflecting from a
> > surface. The ink or pigments on the surface absorb certain wavelengths
> > light and reflect others back to the viewer creating the sensation of a
> > particular color. RGB, on the other hand, is additive color and creates
> > the sensation of color by mixing the wavelengths of light together
> > they reflect off a surface. Technically, when you mix CMY pigments
> > together at 100% you get black, and when you mix RGB light together you
> > get white. When you put ink or pigment on paper you are working in
> > subtractive color ( as a test try mixing red, green and blue ink or
> > pigment together and see if you get white : -). RGB images that will be
> > printed on paper need to be put into subtractive color by outputting
> > negatives of the opposite colors, therefore, the the red channel becomes
> > the cyan negative, the green channel becomes the magenta negative, and
> > on. So, using an analog example of an image of a red apple, red light (
> > passing through a red filter ) exposes the negative film that will be
> > cyan printer. Because the film is a negative, when the cyan pigment is
> > put down on paper cyan will be reduced or absent in the exposed (red)
> > areas allowing the light to reflect from pigment from the other printing
> > films (M+Y) giving the sensation of red.
> >
> > It's late so I hope this makes sense.
> >
> > Jim Morris
> >
> >
> >
> > On Thursday, December 2, 2004, at 06:37 PM, Christina Z. Anderson
> >
> >> My question is this:
> >> with CMYK does the C print cyan, the M print magenta, and the Y print
> >> yellow, as Livick says, or does the C print red, the M print green, the
> >> print blue??? And if C prints C and M M and Y Y, why is that not the
> >> with RGB, too? Mind you, I've never done CMYK seps or felt the need
> >> having come to gum before digineg seps were possible and the option was
> >> color seps in the darkroom with RGB filters...
> >>
> >
Received on Fri Dec 3 09:36:58 2004

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