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, too.
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 a
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 I
was doing my painting degree at the same time. Now I can't even think that
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 get
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 the
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 beginning--stop
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 that,
3 negs with the colors in their right places no matter what system should do
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 RGB.
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 our
exact method because we are just soooo good.

I alway remain open to learning from others. A case in point: in teaching
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 mentioned
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 be
part of her application portfolio.

Gotta love it when students prove you wrong.
Chris
----- Original Message -----
From: "Jim Morris" <jmorris@morriseditions.com>
To: <alt-photo-process-l@sask.usask.ca>
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 and
> is used to create images that achieve color by light reflecting from a
> surface. The ink or pigments on the surface absorb certain wavelengths of
> 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 before
> 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 so
> 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 the
> 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 wrote:
>
>> 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 Y
>> print blue??? And if C prints C and M M and Y Y, why is that not the case
>> with RGB, too? Mind you, I've never done CMYK seps or felt the need to,
>> 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 08:59:04 2004