Re: Color Corrections at a RIP?
Re: Color Corrections at a RIP?
- Subject: Re: Color Corrections at a RIP?
- From: Roger Breton <email@hidden>
- Date: Fri, 23 Jul 2004 08:20:05 -0400
>
1) When printing an RGB image through a RIP, does screening and
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separation of an image occur independently of color correction.
To my knowledge, screening is bound to be the very last operation that
occurs in a PostScript RIP. At least, that's what happens in all 'modern'
distributed prepress workflow systems like Creo Prinergy and the likes.
Now the color question, in my mind, takes place at the same time that
objects are being rendered, one by one. They get pushed on the stack, some
procedure draws the paths and color is converted at that point so that it
can be marked, until the whole page is interepreted and finally plotted.
As far as color correction, I don't quite follow your line of reasoning. To
me, color correction is an event that cannot take place in the RIP unless
you mean the application of transfer function?
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2) Would your answer change if the RIP was sending to an 8-color
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printer?
If it's a PostScript RIP I don't see how that changes my answer.
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3) If one converts to and imbeds a profile for an 8-color printer in
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Photoshop, resulting in a CMYK file, does any information from the
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profile get lost, at all? And I mean anything.
This is interesting. Because ICC profiles, even though they we're modelled
after PostScript Color Management, can't be part of the PostScript stream --
as far as I know. Because Adobe has not endowed PostScript with the smarts
to parse or make use of them. I'm not talking about Extreme PostScript 3
kinds of workflows where jobs can be submitted as PDFs and, as you know,
PDFs support ICC profiles natively, so, there, they are a valid PDF
construct. But, if we mean strictly PostScript, as far as I know, then no,
the profile information does 'get lost' on its way to the printer. It does
not mean that there isn't some kind of intelligence somewhere between the
host and the RIP who handles the ICC profile in some useful way, like in
Photoshop, but I believe if it found its way in the executable PostScript
code, somehow, it would cause a PostScript error immediately.
>
To me, the above questions go right to the heart of modern color
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management in an world populated more and more by inkjet printers that
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use more that CMYK.
Now if we're are talking about RIPs like Postershop from Onyx or BEST or the
superlative Cyclone RIP from ColorBus, then I believe that these have
extensions to make use for ICC profiles embedded in images and they can
convert ICC profiles into Color Space Arrays and Color Rendering
Dictionnaries, effectively transposing the ICC color management in the
PostScript turff. Or, I'm speculating, they could very well execute the
color conversions by calling the OS or their own CMM (Postershop uses
LogoCMM) from within their versions of the PostScript interpreter. Before or
after the job gets processed.
Care to tell me what you have in mind?
>
Douglas Rhiner
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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