Re: Digital Negs - RGB vs CMYK

From: Jim Morris ^lt;>
Date: 12/02/04-11:34:51 PM Z
Message-id: <>

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

> 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 Thu Dec 2 23:35:54 2004

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