Opacity Issues with Placed Items

[Marley C.]

I have experience a potential bug where items that are placed with 100% opacity are appearing to have lowered opacity. After playing around a bit, I noticed that it happens when I change the display performance to high quality. 

Details:

This is a CMYK document intended for print. The blue and black swoop is an .ai file in CMYK, and the image underneath is a high resolution photograph. 

Why is this happening? Is it a bug, or is there a way to fix it? I like to work in high quality display so I can see what the finished product actually going to look like, but this is infuriating. 

[Jeffrey_Smith]

This might be a black overprint issue. Check the Illustrator file and make sure that black shape is not set to overprint.

In Illustrator, Windows > Attribute > Overprint Fill

[Mike Witherell]

Have you considered set the Edit > Transparency Blendspace > to RGB? Later, when you export the PDF, you can choose a CMYK destination.

[Peter Spier · Accepted solution]

You  should also check that you don't have a blend mode like Multiply applied to the .ai file

[Marley C.]

You hit the nail on the head my friend. The black element was indeed set to the multiply blend mode. 

Thank you!!