Quark PDF doubles text black spot layer

[IMPaulyn]

I have created a PDf from Quark 7. Where the alpha channel from an image, overlaps the text, it would appear that in creating the PDF, quark has literally burnt a second copy of the letters on the PDF. This gives the illusion that the text around the image is bolding, but anything far enough away from the image is OK. Unfortunately, our printer has said that there is indeed two lots of text black on the PDF, and it will probably show as bold on the print job. I appreciate that if I were to bring the text to the front of the alpha channeled image, this would not happen, but what is the best way to check. I can just make it out if I turn overprint preview on in Acrobat, but have been unable to print it successfully. We process thousands of pages, and it is not viable to go through each one on screen. I have attached a visual PDf from our printers, which demonstrates the problem.

 

[toronar]

That is a typical "artifact" of transparency flattening. The text gets turned into vector paths where the image's alpha channel overlaps the text.

With sufficient output resolution (1200 or more dpi), the vector paths look identical to the text; less output resolution (like 600 dpi or on screen viewing) and it will appear bolder than the text next to it.
If you zoom in to 1200% or more in Acrobat, you can see that the vector path is identical to the text.

It will print without problems, if the output resolution is high enough. If it is printed on some digital press, the resolution may not be enough. But your printer definately should know about these effects if he uses digital presses and should be able to help you avoid this. "Conventional" printing aka offset or web should be no problem at all with 2400+ dpi (and your printer should know about these effects there, too).

If you want to avoid the bolding effect on lower resolutions (screens, office printers, ...), you have to either place the text above the image (layers are a good way to ensure this) -or- wait till Quark releases the next upgrade to XPress 8 which is rumored to be able to export live transparency in PDFs.

 

[IMPaulyn]

Thanks

Thanks

Many thanks for your helpful reply. Thank you for taking the time to post such an extensive answer.