Open Photoshop file in AI with identical colour space, CMYK numbers change anyways

[BlueCat55]

I am trying to prepare print-ready files for a poster, according to my printer's specifications.

The poster was originally created in Photoshop. However, because my printer wants a PDF with a specified bleed, I'm trying to transfer the artwork into Illustrator so I can set up print-ready files with bleed marks. My original PS file is in working CMYK, and so is the receiving AI file I've set up to receive it. However, I cannot seem to move the Photoshop artwork into Illustrator without the CMYK values for all colours changing. I have tried drag-and-drop, saving the artwork as a TIFF and as a PSD and opening it in AI, saving it as an Adobe PDF and opening it in AI, and both linking and embedding the artwork into AI as an image, and nothing has worked.  As an example- in the PS file, all of the text on the poster is 100%K black. But when I move it into the illustrator file, in the exact same colour space, it changes to a strange breakdown of rich black full of decimal values. This is happening with all of my colours- the CMYK numbers are changing to a strange set of decimal values.

Some techincal details:

The original poster file in Photoshop is in working CMYK, U.S. Web Coated (SWOP) v2  8bpc. The artwork has been flattened into a single layer. Before flattening, I edited the CMYK breakdown/total ink coverage of my colours with a Channel Mixer adjustment layer, but never touched CMYK settings for the actual document.

The receiving Illustrator file, into which I'm trying to move the artwork, is also working CMYK, U.S. Web Coated (SWOP) v2.

My Colour Management Policy in AI, for CMYK, is set to Preserve Numbers (Ignore Linked Profiles). (I also tried with it set to Preserve Embedded Profile, and it didn't work either.)

I'm viewing the colour separations in PS using the Info Panel.

I'm viewing the colour separations in AI using the eyedropper/colour panel.

The version of PS I'm running is CS5.

The version of AI I'm running is CS4. (long story. I have an old, patchwork suite.)

Any ideas why the CMYK numbers won't stay the same between programs, if the working colour space of both files is the same? Could it be an issue with the "Embed ICC profile" option when saving the PS document? (In the cases where I tried saving and opening it?) I've heard that the eyedropper in AI can be funny sometimes- is my AI eyedropper/colour panel simply not displaying the correct numbers? Could it be a bug resulting from trying to use two different versions of Adobe Programs? (For the record, I've moved things from PS CS5 to AI CS4 before and never had a colour conversion problem before this. So could I be looking at a program corruption somewhere?)

Please help! I'm at my wits end as to why this should be happening.

[Monika Gause · Accepted solution]

Save that Photoshop file as PSD.

Then place/link it in Illustrator.

Don't try and sample color at that moment, doesn't make sense.

Then save the PDF and watch out for the color settings in the color management tab. Needs to be set to "Preserve colors" as well.

Then open the PDF in Acrobat.

Watch out for the profile setting in the print production/Output dialog box.

Sample colors.

[BlueCat55]

Thank you!!!!!!!!!!!!!!! It worked! 

I kept my AI CMYK Colour Management set to Preserve Numbers (Ignore Linked Profiles). I placed/linked the PSD into Illustrator, added my bleed, and then saved it as a PDF with "No conversion" and "Don't Include Profiles" in my Output settings. (I assumed that was what you meant by preserve colours? Since I'm thinking that this would just keep the raw numbers with no profile interpretation? Is this correct?) Then I previewed the Output in Acrobat, under U.S Web Coated (SWOP) v2 (my original PSD colour profile), and- hooray!- all of my colours are showing the correct breakdown that I intended. Saved as a PDF-X1a for U.S Web Coated (SWOP) v2.

So the colour data appears to be correct for the intended end-use of my final output PDF- unless you see any calamitous errors in what I did?

As an aside, I'm curious as to why the Illustrator eyedropper didn't properly sample the colour breakdown- is this just a bug?

[Ton Frederiks]

In an Illustrator CMYK document with CMYK images:

The Illustrator Eyedropper samples an RGB preview when the images are linked.

The Illustrator Eyedropper samples correct CMYK values when images are embedded.

[BlueCat55]

Ahh- that makes sense. I didn't realize that the preview was RGB.

Strangely though, the numbers were still off even after I embedded the image. I've since tried this again with another PSD (different from the original file I was working with). It contains, among other colours, a rich black, 50,50,50,100, which, after embedding in Illustrator, samples as 49.8, 49.8, 49.8, 100. Certainly a lot closer than what the RGB preview spits out (when linked), but still not right. I've tried placing this PSD in a new document 4 times, each time using a different AI CMYK colour management policy, and the results are the same. (This new PSD I've tested differs from the original in that it has no embedded ICC profile. But the original file, with a profile, did not embed accurately either when I first tried.)

Not sure what that's about. Regardless, the next time I need to place external files in AI, I'll be relying on Acrobat to check the colours.

[Ton Frederiks]

Looks like rounding the numbers (and nobody will notice the difference between 49,8% and 50%).

Try this:

Place the file embedded and sample the colors, you get:

49.8, 49.8, 49.8, 100

Create a new rectangle and fill it with that color.

Copy the rectangle ceate a new Photoshop file and paste as pixels:

Sample the color.

You will get:

50, 50, 50, 100

[Test Screen Name]

For some unknown reason, CMYK values are shown as percentages, but they are stored in images as numbers from 0 to 255. This gives rise to some interesting rounding effects. This means that there are no exact numbers. Colour values stored as 127 and 128 are about 49.8% and 50.2% Either one might be shown as 50% because it gives people a happy glow of spurious exactness. In vector art, CMYK values are numbers between 0.0 and 1.0, so 0.5 is entirely possible. But don't sweat rounding errors.

[Ton Frederiks]

Correct, good you added the explanation.

[Kat Gilbert]

I recently had this same issue--- very frustrating until one clears the avenue of direction!

[Jacob Bugge]

LAOPeroxide, others,

I believe the use of process/CMYK colour percentages makes good sense for ease of determining total ink coverage, mentioned in the OP (and also because the strangeness that may feel like an inconsistency.

As a curiosity, RGB colours only appeared in 7.0, the original Paint Style options being None, White, Black, and Process color with CMYK in percentages of course, no Color Mode.

[Ton Frederiks]

When Illustrator was developed, the idea was to specify color as RGB values with 6 digits.

John Warnock listened to designers (like Luanne Seymour) and it became colors that could be defined in percentages of CMYK.

As Jacob said, RGB was added later in version 7 (together with ICC color management).