Illustrator colour models

[Adrian]

Hi!

We have just sent a specimen of a job we're working on to the printer as PDF files, and there seems to be a problem. It's a two-colour job, with mono (line or greyscale) illustrations. The printer is saying that (some of) the illustrations are CMYK and that this is a problem. We have looked at one of the illustrations in Illustrator CS2, and the colour mode is indeed CMYK. But it has only two options: CMYK and RGB. If we convert the eps illustration to greyscale in Illustrator, the converted illustration still has the CMYK colour mode. Common sense tells me (I'm not an Illustrator expert!) that it must be OK for the illustration to be in CMYK colour mode and be grayscale, and that it should therefore print in black only. Is the printer (who is in Spain, and with whom we are not in direct contact!) reacting to a "label" of some sort in the eps illustration file, or is there something more sinister going on here?

Best wishes, Adrian

[Wharfrat]

Did you actually build the files in Illy CS2
or open earlier versions of Illustrator in CS2 and save?
The files are not "embedded" Photoshop files?
CS2 solved many problems with "build" blacks
and CMYK "embedded" links.
Chances are your printer is correct -
can you post a file or two somewhere for us to see.
If you tagged your files with a different profile than the printer would use,
there would be a conversion such as you see.


MSD

[Adrian]

Wharfrat,

All very good questions! After much digging, we discovered that although the artist had revised the illustration in Illustrator (a pre CS version) she had originated it in Photoshop, where, although it she had used only black and tints, it was specified as CMYK. When we printed it on our desktop laser as separations, we got four prints.

The first part of that makes sense to me, but I still don't undertand how the black separated into four colours!

Also, given that Illustrator categorises all images as either CMYK or RGB (i.e. no greyscale option), we presume that a mono image with a CMYK colour model is not a contradiction. So how do we know if we have a problem image?

When we collected this job for the printer in InDesign CS, some of the reports said that we were using four colours, some said two (it was a two-colour job). We test printed all of the image pages and they were all mono black. Even when we went back into InDesign and deleted all of the unused colours, we still got the report that said we were using all four.

Is this an InDesign feature? Or are some of these images carrying a CMYK identifier somewhere/somehow?

I think we're making progress, but I'm not sure that I feel fully in control!

Best wishes, Adrian

[Wharfrat]

From your desktop laser - you would get 4 prints for CMYK -
even if the CMY were blank.
An RIP is generally "smart" enough to send only the used colors
on to the Imagesetter or Platesetter.
-
If any file is "embedded" into Illustrator (this has changed in CS2)
it instantly becomes CMYK (or RGB). Your pure Blacks will become
process build Blacks.
If you know your Photoshop file is Black only (or any spot color/s) -
you must "link" your file to your Illustrator file - not "embed".
-
Any color can have a CMYK or RGB definition.
-
When you place the file into InDesign -
use your "Separations Preview" to see how and what will print.
Also - always have "Overprint Preview" activated
when using InDesign or Acrobat.
-
Reporting the process colors as well as the spot colors (or just black)
is standard.

MSD