Placed PDF causes change in greyscale images

[matthewr45162948]

I have a magazine design that is exported to PDF for a commercial printer to create proofs from. There are a number of greyscale images in the document that print fine for the most part. The only time they do not print correctly is when there is a placed PDF file on the same page (typically an ad). When this occurs the greyscale image that shares the page prints lighter than expected. All other greyscale images in the doc print fine, it is only when a placed PDF shares the page does the error occur.

My guess is that there is something in the placed PDF (it's color profile, transparency settings, black settings, etc.) that is affecting the greyscale images on those pages only.

Anyone have any ideas how to fix this?

[Rishabh_Tiwari]

Hi,

Thanks for reaching out. I found this similar discussion https://community.adobe.com/t5/indesign-discussions/placed-pdf-over-inking-on-export/m-p/12064895#M4... which you can refer to and let us know if this helps or if you need any further assistance.

Regards

Rishabh

[matthewr45162948]

Thanks Rishabh -- while not 100% solved, this definitely seems to be related to the issue. Looks like it's something related to either the Transparency Blend Space in my InDesign doc, the transparency blend mode used by the advertisers to create their PDF ads which are then placed into the InDesign doc, or the transparency blend space of my final export.

[rob day]

Hi @matthewr45162948 , can you share the PDF? You should be able to attach it to your reply.

[matthewr45162948]

Unfortunately I cannot due to client NDA agreements.

[rob day]

There are a number of greyscale images in the document that print fine for the most part.

Not sure we can help without inspecting the PDF.

There are a number of greyscale images in the document that print fine for the most part.

If you check the grayscales that print fine on the press sheet under a loupe are they black only or have they been converted to CMYK (you are seeing CMY dots in the B&W image)?

[matthewr45162948]

Completely understand, no worries.

[rob day · Accepted solution]

From your description it sounds like the PDF "grayscales" have been converted to CMYK, which would account for the darker tonality, and the placed grayscales are making it through to the press sheet as black only. Normally placed grayscales preview as they would print on the CMYK black plate when Overprint Preview is turned on.

Usually there is no conversion on a PDF export, the exception would be if the PDF export was to a CMYK Desination profile that conflicts with the assigned document profile, or the Transparency Blend Space is set to RGB and the Export is to a flattened preset, e.g. PDF/X-1a. You should be able to see that on the press sheet with a magnifier.

[matthewr45162948]

I believe you are correct—it is due to the Transparency Blend Sapce being set to RGB and exporting to CMYK. Combined with placed PDF ads that we have no control over. Thanks!

[Jumpenjax]

Extract that page, open in photoshop, make sure you open in RGB or cmyk which ever you need. Then flatten and save as a tiff.

[matthewr45162948]

Unfortunately I cannot do this as all pages have to be released to the commercial printer as PDFs not tiff.