Can flattening a PDF cause a color shift?

[Jonlin Creative]

Hello all,

I've got a client who is self-publishing a series of books via Amazon KDP. The cover design uses the same colors across all the titles with just a change of image on each book.

For all the volumes, I've exported a PDF of the cover art and all was well. For the latest volume, KDP told my client the PDF should be flattened. I did that. But when she got her proof copy back, there was a notable color shift in the yellow we're using.

I checked my files and there was no color change. The color values show the same in Acrobat in both the flattened and unflattened versions of the document. They look the same on my screen. But they clearly don't look the same when KDP prints them.

Is this a known issue? Or is it just a coincidence that it's happening now and is actually caused by something else (e.g., some other change on the printer's end)? My client asked KDP about it and didn't really get any useful info.

Any thoughts?

[JR Boulay]

What did you flattened?

Forms fields?

Comments?

Transparencies?

Layers?

[Jonlin Creative]

I had an InDesign file for the book cover. The front cover had been done in Photoshop and brought into InDesign as a PDF. The back cover and spine were typeset in InDesign and then I exported a PDF file using PDF/X-1a with compatibility set to Acrobat 5

In Acrobat, I used the Flattener Preview to flatten the file. I set the raster/vector balance to 90, checked the box to convert all text to outlines, and if I remember correctly, unchecked the box for clipping complex regions.

There were no form fields or comments.

[Abambo]

Why exporting to X-1a when you could use X-4? Flattening could for sure have an influence on the colour, if the Data is weird.

[Jonlin Creative]

X-1a was the recommended option at one point and I've been using it for years. I guess I never really thought about changing. 🙂

So when you say "if the data is weird," what do you mean? And what about the fact that the color values are the same in Acrobat? It's only shifting in the printing process.

[MikelKlink]

Which color spaces do you use in your document?

[Abambo]

The colour profile used may be the culprit, if the shift is only at the proof print. Check with prior PDF data.

If transparency is used, you also could have colour shifts. When Spot colours are converted to CMYK you could have colour shifts. 

If I understand you well, you had books printed before, and the colour was different and "correct"? I would check if there was a change in the production process on your side. If before, eg you did not flatten the file, may be they did it, before printing.

There may also be a very easy simple explanation: your print provider may have acquired a new printing machine.

[Abambo]

X-1a was the recommended option at one point and I've been using it for years.

By @Jonlin Creative

X-1a basically is outdated. The standard is from 2003, so there are 20 years in between. A standard printing service should be able nowadays to handle PDF/X 4 which is much more capable.