Color definition problems

[Ridder, Fred]

The simple fact is that there is no direct translation from CMYK to
RGB because these different color models are built on a totally
different basis in physics. RGB is an additive color model because
you're dealing with points of light (glowing phosphor dots on a CRT
or back-lit crystals on an LCD). CMYK is a subtractive color model
for ink-on-paper reproduction. The color you see is a result of all 
the wavelengths that are not absorbed by the ink, which is why 
it's called subtractive; the ink subtracts out all undesired wavelengths
from the (presumably) while light that illuminates the page.

The problem is that RGB can only simulate CMYK because the 
models are so fundamentally different, and there are dozens (if 
not hundreds) of different mathematical algorithms for how to
translate values in one model to the other. 

The one thing you know when you work with CMYK color
definitions is that if you make color separations and furnish the
films (or files) to a print vendor, you'll get the same results 
regardless of what tool you used to generate the separations.
But it's virtually guaranteed that the printed results will match
*neither* tool's on-screen simulation of the color. Probably not
even close. 

If you're trying to design a CMYK color that has a particular
appearance, the only right way to do it is to work from printed
samples and then simply live with whatever screen representation 
you get in a particular tool. Or if the color is only being used
as a spot color you can use the Pantone color matching 
system (or an equivalent) where you pick a color from a 
set of swatches and refer to its reference number when you 
provide your job specifications to your print vendor. 

My opinions only; I don't speak for Intel.
Fred Ridder (fred dot ridder at intel dot com)
Intel
Parsippany, NJ



-----Original Message-----
From: framers-bounces+fred.ridder=intel.com at lists.frameusers.com
[mailto:framers-bounces+fred.ridder=intel.com at lists.frameusers.com] On
Behalf Of Gillian Flato
Sent: Thursday, August 17, 2006 8:12 PM
To: framers at frameusers.com
Subject: Color definition problems

Gurus,
 
When I create a graphic in Adobe Illustrator and I enter the CMYK color
definition of 100,0,76,15, it displays as dark green. When I enter those
same CMYK settings in the Color definition area of Frame, it comes up as
a Kelly green. They aren't even close. What is the problem? Why are they
so different? How do I fix this?
 

Thanks,

Gillian Flato

Technical Writer (Software)

NANOmetrics, Inc.

1550 Buckeye Dr.

Milpitas, CA. 95035

(408.435.9600 x 316

7  408.232.5911

* gflato at nanometrics.com <blocked::mailto:v at nanometrics.com>