New subject: Things about color management that are not clear

9 Dec 2011

      Hi Thibaut,

a lot of questions, which might be answered best at a thorough local training at your
site, as Jan-Peter said. Without knowing your specific problems, some guidelines:

1. OutputIntent in PDF/X is to communicate the intented color representation of the
graphics. You might print to some very different papers, which can't be simulated (or
even unknown) to the submitters of your graphics files. So it's easier for all of you
to acquire data in a standardised color space (eg.: ISO Coated v2, aka FOGRA 39), which is
well known now for of the graphics artists.

2. In your in-house production workflow you might use PDF/X and OutputIntents, but at your
level it's not really necessary, because you always know the output color space (which
is defined by the material you're printing on, the used inks and other process
parameters). So a good practice would be to specify FOGRA 39 / ISO Coated v2 as the
submission color space for your clients, but work in Illustrator in your final printing
color space. You may mess around with OutputIntents if you have a lot of various materials
to print on (and you have their ICC color profiles), or if you have a large staff and a
sophisticated workflow. Otherwise the best would be to define each job's color space
in a job ticket right at the start, and use that info throughout the production, and leave
PDF/X alone, at least in-house.

3. Working in your specific, job-based CMYK color space is a must in the packaging
industry. This helps you avoid most of the problems which may arise at the time of
printing, and of course helps you softproof your jobs in CS application (provided you
assigned the correct ICC profile to the document).

4. The difference between 'Convert to Destination' and 'Convert to Destination
(Preserve Numbers)' is that the former mode always convert colors if they differ from
the chosen output color space, while the latter doesn't. Example: you placed an image
to InDesign, which has the color profile "SWOP v2" embedded. You output the
design to PDF and choose the destination to be ISO Coated v2. "Convert to
destination" will re-separate the image from SWOP v2 to ISO Coated v2 during the
process, but the 'Preserve Numbers' will not: it will retain the exact separation
of the original image. What's the catch? If you get images in a wrong color space, you
might think that all of them must be converted. Alas, CS applications perform an ICC-based
conversion, which means the black separation data will be lost – all the black type (and
black-only elements) will go CMYK, they will be present in all separations. This is a
disaster in most cases.

5. Sorry to say, the behavior of the 'Convert to Destination (Preserve Numbers)'
option is somewhat different in CS applications and versions. That means CS2 Indesign may
produce a different PDF than say CS3 Illustrator with that option choosen. This is why I
suggest you to leave the conversion in InDesign or Illustrator alone, and use the
'Don't convert' option (of course this way you have to be sure that all placed
graphic is in your output color space).

6. How to handle overinking, and different color spaces? The solution to that is to
manually re-purpose, re-separate all incoming graphics with some very clever approach in
Photoshop, or to use a device-link conversion engine, which can put the graphic to a
different color space, while retaining the black separation.

7. PDF/X-4 is very important to you, as a properly authored file can contain the source
data in a very abstract form. That means your task in Illustrator is much easier (the
images are intact, all the graphic elements are intact and movable, there's no
flattening applied, which might ruin the editability). I would say that the best for you
would be to specify PDF/X-4 with OutputIntent: ISO Coated v2 as your preferred incoming
data format.

Kind regards,

Peter Nagy
Colorcom Media
Budapest, Hungary

Re: [ECI-EN] Things about color management that are not clear