Re: Colorsync-users Digest, Vol 6, Issue 190
Re: Colorsync-users Digest, Vol 6, Issue 190
- Subject: Re: Colorsync-users Digest, Vol 6, Issue 190
- From: Brian Lawler <email@hidden>
- Date: Fri, 14 Aug 2009 12:38:56 -0700
Hi all,
In response to Matthew Kelly's comments (in response to my earlier
comments):
I had posted a post-mortem on this earlier, a result of my long
conversation with Dov Isaacs at Adobe.
Here is a quick summary:
1. When you "Convert to Destination (preserve numbers)," InDesign
leaves untouched:
a. all CMYK created within the document (text, graphics)
b. all CMYK images that are already in the destination color space
c. all CMYK images that have no embedded profile at all
d. all CMYK placed illustrations that have the same CMYK profile as
the destination profile
Everything else will be converted to the new CMYK color space:
a. all Lab color images
b. all RGB color images (regardless of their embedded profile). It
does use the source profile for calculations, however
c. all CMYK images that have a different color profile embedded than
the destination profile
d. all placed illustrations where the color profile is different than
the destination color profile (RGB or CMYK)
2. When you choose "Convert to Destination," InDesign will:
a. convert all CMYK to the new CMYK. This does not include any CMYK
with the same CMYK profile as the destination profile
b. all Lab and RGB color to the destination color profile
3. When you choose "Don't include profiles," InDesign will:
a. make the conversions above, and will tag each and every element
with a DeviceCMYK tag, indicating that it is CMYK color that has no
specific profile. This turns out to be the safest way to handle this.
i. DeviceCMYK is a reserved word to a PostScript or PDF RIP. It
means, "Don't touch!" and it results in color going through the
prepress system without modification.
4. When you choose "Include destination profile," all hell breaks
loose. InDesign converts (according to the instructions above) and
then ALSO tags each and every item in the document with the chosen
destination profile name, and it embeds the profile in the document.
This is where I got in trouble. My printer was taking the PDF with the
tags embedded, and exporting them to EPS for a Rampage RIP. That's
fine, except the act of exporting to EPS is itself a color management
event! If you fail to tell the EPS exporter controls that you are not
simulating a different press (SWOP, for example), then it will
reconvert EVERYTHING from the CMYK chosen in InDesign to the CMYK
default in Acrobat Pro.
If you tell it to simulate the same press profile as was used to make
the conversion from InDesign, then nothing will happen. If it
reconverts the color another time, then it will double-color correct,
and it will turn 0,0,0,100 into 37,43,34,79 (or something similar
where you have a 4 color black). Disaster!
SOLUTIONS:
1. Don't embed the destination profile! (this will result in
DeviceCMYK tags). This results in a CMYK that will pass-through most
prepress systems untouched.
2. If you embed the profile (and thus tag all of the elements in the
PDF), then you MUST "simulate" the same profile when either printing,
ripping, or exporting to EPS.
For the latter, use Output Preview in Acrobat Pro's Advanced menu.
Aren't you glad you asked?
For more details, including charts and graphs, please see my blogs at
Graphic Arts Monthly magazine online.
Best wishes,
Brian P. Lawler
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