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Re: How to do RGB to CMYK conversion for PS output? [message #49386 is a reply to message #49317]

Sat, 15 July 2006 12:31

George N. White III is currently offline

George N. White III
Messages: 56
Registered: September 2000

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On Thu, 13 Jul 2006, David Fanning wrote:

> Paul Van Delst writes:
>
>> A colleague produced a colour X-Y plot for a paper and saved it to a
>> regular old PS file. The editor mailed back stating that the file
>> contains RGB colours and could we please create the file in CMYK
>> colours.
>> [...]
>> Any ideas?
>
> Photoshop?

Yes. There is generally a significant difference between the CMYK you get
using Photoshop and from IDL. I think IDL uses the simple formula:

C=255-R ...
K=min([C,M,Y])
C=C-K ...

This seems reasonable in theory, but in practice CMYK devices have a
restricted gamut compared to typical (CRT and LCD) displays. Different
printers handle out-of-gamut values differently, but most will give muddy
looking colors with CMYK images created by IDL using a color palette that
looks good on a display. Photoshop generally does a much better job (and
will show you which colors are outside the CMYK gamut). For best results
you need color profiles for both the display and for the output device.

--
George N. White III <aa056@chebucto.ns.ca>

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[Message index]

		Re: How to do RGB to CMYK conversion for PS output? By: Paul Van Delst[1] on Thu, 13 July 2006 12:55
		Re: How to do RGB to CMYK conversion for PS output? By: Karl Schultz on Thu, 13 July 2006 12:23
		Re: How to do RGB to CMYK conversion for PS output? By: David Fanning on Thu, 13 July 2006 11:46
		Re: How to do RGB to CMYK conversion for PS output? By: George N. White III on Sat, 15 July 2006 12:31

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