Hi,

I have been using illustrator for some time now and preparing graphics for print without problems. It was only recently though that a typestting company we use informed us that we should be saving all our images with the 'Do***ent color mode' set to CMYK in illustrator even though all of the objects in the image were already CMYK.

I had never really used the 'color mode' before and have never been aware that this could affect the outcome of the printed job.

Isnt it simply a preview? (any help appreciated but please dont reply if youre not sure...)

The doc colour mode will affect the colours within the file. Try a test with a filled box and convert to the other mode and ****yse the CMYK values - they change. If the vendor opens the RGB file and converts to CMYK the colours will change also. The Spot colours should not be affected by the coversion, however.

There is a seperate function (under View) to set up the actual preview, and this depends on the profile the file has (which simulates the colours on how the job is to be printed - sheetfed, web etc.) The file profile can be accessed via Edit>Assign profile. For this to be accurate you also have to setup the Colour Settings (under Edit) and use the calibrated monitor profile.

Even if the colour palette says an object is CMYK, this is just the CMYK equivilent of the RGB object in the RGB file; it doesn't mean it's actually CMYK.

You're right, the values do change when converting to and from CMYK and RGB in Doc Colour mode, but would a client need to convert the files if they were all saved as .eps with CMYK postscipt option?? ie: could the fact that it is set to RGB cause problems when printing (usually to pdf)?

if not, would it not be better to leave the files 'as is' as you (correctly) state that the colour changes upon conversion? thus leaving the files as close to the authors original as possible.

I did try the conversion as you suggested and after repeatedly flicking backwards and forwards a number of times (7 or 8) between the 2 modes (CMYK and RGB) and watching the sliders move a fraction each time it went back to CMYK they eventually reached a point where the colour no longer altered?!?!

I dont know, just when I thought I had a grasp at Illustrator and Colour in general along comes this....

thanks for your help by the way...

The CMYK option will allow apps that do not support RGB to output RGB files. If an object in an RGB doc is set with a CMYK colour and saved with the CMYK option as EPS, when the file is reopend these values change once again.

If the file is destined for press output (as opposed to web), just start with a CMYK doc. Save as EPS with the CMYK option checked, and fonts embedded. Then distill to PDF with the appropriate job options (there are a lot of settings to contend with in Distiller regarding colour workflow) but with a bit of trial and error you can get a reliable PDF which will go to press with out any problems.

If you are using the CS package Acrobat will also give you on-screen separations (Advanced>Separation Preview) where you can turn each plate on/off to ensure the black, for example, is 100% black. If not then print separations from AI through the options in the print dialogue box.

Don't worry, it is a can of worms!

The reason you may never have noticed it before is that Ai didn't have two mode options before AI10(?).