Let me see your link
I actually had no choice untill now. People I'm working for used to send me their pictures in .png (Keyshots pictures). But I'm going to ask them .tiff now. It should solved the problem.. Shouldn't it?
No, TIFF will have the same problem, but TIFF can support colormanagement, PNG cannot.
Hm I see.
But how come this problem appeared suddenly? Did I do something wrong?
Well, problem is still there but not only with InDesign but with all PDF created (I just tried with a converted .ppt in .pdf). Well, I'm going to try to find an answer somewhere else as the problem doesn't come from InDesign..
Thanks again for your help!
What version of InDesign are you using? What are the exact export settings?
PNG files should be fine if you're using screenshots.
Well, I'm going to try to find an answer somewhere else as the problem doesn't come from InDesign..
You are printing to a composite printer right—this isn't a separated workflow to an offset press? What you are showing is probably a symptom of bad transparency flattening at output.
When you export to Press Quality the transparency is kept live and all of the color is converted to your document's CMYK space. Because the transparency is kept live you don't see the problem in the PDF, but chances are you are still flattening in the Acrobat print dialog, which is introducing the artifacts in the print.
So you can try handling the flattening on export (PDF/X-1a), which would be the easy way to find out if the problem is flattening related, or you can make a custom flattener preset in Acrobat with a high raster balance (see Willi's link).
Here's how to make custom flatteners in AcrobatPro:
You shouldn't have this problem if you export to PDFx4 2010
When I export my document in "PDF press quality", I can see layers of all .png I used in transparency
Do you see the screened boxes in the PDF, or is it just in the print output?
Sorry for answering that late. Well, I followed your advices, and I finally exported as PDF/X-1a and changed the options of screening (as Roba Day saw me) and it works!! I just need to create custom PDF presets now.
Thanks a lot (to all) for your help