I'm about to send some artwork to print and noticed on the logo which has some transparency, displays a faint outline around each triangle.

The artwork was designed in Illustrator CS5 (CMYK), saved to PDF ready for print under presets [High Quality Print]. The outline does not appear on the saved PDF or in Illustrator, only seems to occur when transparency is flattened.

Business Card Front

Is this a screen display issue, or can it be ignored? My only worry is when zoomed in, the outline still appears.


3 Answers 3


Do not trust the on-screen display of a print-ready .pdf. Ever. Seriously, any and all .pdf viewers have huge problems rendering print-ready .pdfs on-screen.

One of the common rendering errors is indeed with hairlines between areas of different opacity, or intersected by areas of different opacity or blending. Mostly, these hairlines are artefacts of the rendering you can safely ignore when sending your document to your printer.

To be absolutely sure, you can always zoom in on such a hairline--they will be just a single pixel wide, regardless of the zoom percentage. If the gap does scale with zooming, then there's something else amiss.

These rendering errors in most (if not all) common .pdf viewers has made me decide to never, ever send a print-ready file to a customer for final approval. They always approve a version optimised for screen display, while the printer receives the actual cPDF.

  • Do you recon there is any disadvantage to using a Hi-Res JPEG to send for print?
    – Tom25
    Oct 7, 2014 at 16:34
  • Yes. No printer's marks, no colour management profile, no vector (nasty for small text), and file size for large formats (think billboard) are just a few off the top of my head.
    – Vincent
    Oct 7, 2014 at 16:36
  • No possibility to include other inks than CMYK or die-cut shapes come to mind as well. That comment of yours could make a nice question. I'd upvote it.
    – Vincent
    Oct 7, 2014 at 16:39

In addition to what has been said you can use Object>Flatten Transparency. A lot of different outcomes may come out of transparency depending on the RIP engine your printer is using.


Easy solution, export artwork as a JPEG with maximum quality.

  • Hi Tom, welcome to GDSE. Unfortunately, I do not see how this answers the question in any way. Yes, the lines will disappear on this export setting, but a hi-res jpeg is hardly print-ready, no?
    – Vincent
    Oct 7, 2014 at 15:22
  • 1
    Hi Vincent, since there was no answers. I gave a solution which for me is better than '0' answers. A well known printing firm within the UK recommended to export the artwork as JPEG to prevent the transparency flattening issue. I'm not sure why this is the case, but if you know - prey tell...
    – Tom25
    Oct 7, 2014 at 16:09
  • Ah, it's only now that I see that you answered your own question. I'll try and come up with my own answer.
    – Vincent
    Oct 7, 2014 at 16:23

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