Re: Re(4): embedded profiles in PDF/Postscript
Re: Re(4): embedded profiles in PDF/Postscript
- Subject: Re: Re(4): embedded profiles in PDF/Postscript
- From: Roger Breton <email@hidden>
- Date: Fri, 04 Jun 2004 21:22:34 -0400
Dear Olaf,
>
any PDF/X file - whether PDF/X-1a or PDF/X-3 (or even PDF/X-2) - must
>
have a (document wide) OutputIntent that describes for which printing
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condition the PDF/X file has been prepared.
OK. I am glad to hear that the spirit of the PDX/x-1a standard is to have
some colorimetric reference in the PDF/X document for the purpose of
identifying the particule CMYK printing conditions the colors are intended
for. That is my understanding.
>
If the PDF/X file only
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contains CMYK or Gray (without ICC profiles), the OutputIntent may simply
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point to a printing condition that is registered with the ICC registry,
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but it may (in addition or instead) contain a CMYK printer profile to
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describe the printing condition.
I am shocked to hear this, Olaf. I was under the impression, from my limited
PDF/X-1a reading, that the OutputIntent ICC profile MUST be embedded in the
PDF/X for complete compliance? What you say is that it is not mandatory. If
the user only puts in a reference to "some" printing condition that is
registered with the ICC registry, then this is opening the door to avoid
taking responsibility for the color in the document? People in America will
simply refer to CGATS TR-001 when in actuality the CMYK colors in the PDF/X
really does not have any relationship with CGATS TR-001. That's an
unfortunate shortcoming.
>
For PDF/X-3 (and for PDF/X-2) files that use device independent color
>
(ICC based colors, Lab or CalGra and CalRGB), an ICC printer profile in
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the OutputIntent is mandatory.
OK for PDF/X-3 but we're not there yet. People still have not finished
digesting PDF/X-1a, let alone PDF/X, it seems.
By the way, may I ask what CalRGB and CalGray are? Are these actual Adobe
ICC profiles? I think these are used in PDF 1.2 (Acrobat 4 files).
>
As a PDF/X-1a file never must contain device independent color, the ICC
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profile in the OutputIntent is optional as long as there is a valid
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pointer to a printing condition in the ICC registry.
Yes, that is fine and dandy but this really leaves me on my appetite for
color management leadership. So the real color hero of the PDF/X standard is
PDF/X-3 because in X/3 the CMYK OutputIntent must be specified and will be
used to carry the final CMYK separations.
>
For practical purposes it typically makes sense to always embed a printer
>
profile in the OutputIntent,
Ah! Now, we're getting somewhere. It makes sense but it is not mandatory.
How prelavent, in your opinion, is the practice of embedding an OutputIntent
ICC profile in PDF/X-1a files? In Europe? In America?
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as a lot of tools and systems can pick it up
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and do useful things with it, like a proof simulation (or a starting
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point for a CMYK to CMYK conversion, if the file has to be printed in a
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different printing process, e.g. offset instead of gravure).
I agree 100% that it is a very responsible thing to do. Just like embedding
CMYK profiles in CMYK images. ;-)
>
Olaf Druemmer
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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