When You See Thin White Lines in Your PDF Files

Have you ever opened a PDF file and seen thin white lines where there shouldn’t be any? In general, the white lines, or “light leaks” are due to a PDF that includes flattened transparency — transparency effects (such as placed PSD files) in a file saved in a file format that doesn’t support transparency (such as Acrobat 4, a.k.a. PDF version 1.3).

Flattening transparency means “faking it” by creating opaque areas that look transparent. But these opaque areas have to fit together like a mosaic, each piece right next to the next. The result is that sometimes white peeks out between them. In the vast majority of cases, this appears only on screen! Sometimes it shows up on low-resolution printers, too, but virtually never in high-res commercial output.

See the thin white lines around the trapazoid at the top and around the text at the bottom?

White lines

The best trick I ever learned for dealing with these came from Michael Stoddart, who said: Zoom in and out! If the white lines are always one-pixel thick (they don’t get thicker or thinner), then they are just screen artifacts and you can probably ignore them. If they do get thicker when you zoom in, then they’re really there.

This used to be a huge problem, but it’s gotten more rare as time has gone by. I think the reason it’s rare to see this is that Acrobat has gotten smarter. In fact, I can’t even force Acrobat 9 Pro to show me those lines in the image above. I opened the PDF in Mac OS X Preview. There’s another good trick: Never assume Preview (or any other pdf reader) is giving you an acurate, um, preview.

If you do see white lines in Acrobat, check the Page Display preferences, and make sure “smoothing” is turned on:

Acrobat Prefs

There have been other issues with white lines, such as this old CS3 problem with PSD files (which I haven’t seen in a long while) and this even older bug in CS3. But again, those don’t show up much anymore.

Tags
Related Articles
Comments

65 Comments on “When You See Thin White Lines in Your PDF Files

  1. Those lines can happen even in CS6 and Acrobat 10. Check to see if you’ve placed any FX on a group. For example if you group some objects then put an inner shadow on the group, you may end up with those hairlines. The alternative way to get that inner shadow and avoid the hairlines is to remove the shadow on the group, place a white box over the group, put the shadow on the white box, then set the box to multiply. The white disappears, the shadow remains, and no white hairlines will be on your PDFs, no matter what version.

  2. This problem is inherent to Acrobat and easy to solve. Open the preferences panel. Click on “Page Display” in the right column named “Categories”. In the “Rendering” section, make sure that “Smooth line art” is unchecked. There you are, the ghost lines should disappear.

  3. it is happening to me with gradients in illustrator. When I save the logo as an EPS and then view in Acrobat there is white pin lines all over it. I am using CC so, you would think this would have been fixed by now. Now the client is asking for an EPS and I have to hand over something that is less then the perfection they are paying me for. I know that I just have to explain that the lines won’t print but it still sucks to have to deal with it.

  4. Yes!!! I been trying to fix this for a couple of hours now, trying everything and (almost) going a bit crazy in the process. Now, thanks to you, problem solved… pheeew :)

    Thanks buddy!

  5. I am stuck, I am getting white lines on artwork (placed psd files in to indesign CS4) that don’t disappear when I scroll in. I have tried to uncheck the smooth line art box but is not highlighted so I can’t uncheck it. Please help it is driving me mad!

  6. I had the same problem using ID CC and Acrobat 10, but the white line turned to a cyan and magenta line in the rip to plate process. The client had set transparency to low, so I set it on medium, PDF with no “X” and it has worked fine now.
    Odd that the apparent “phantom white line” actually turned into a line in the RIP process.

  7. I have a psd file with transparent background placed in Indesign. Under the image, I have a blue shape, and I have the stitching going through the image where the stroke of the shape would be. I’ve printed it out on my own machine and the lines do show up. I hope they won’t show up in print, as you say the don’t show up on commercial grade printers. Would love to try un-checking the ‘smooth line art’ option so many of you recommend, only the option is grayed out by me. I have no idea how to get that changed.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>