In all versions of QuarkXPress, PostScript output can give a better final result in the following situations:

• When placing a PSD file with an alpha mask
• When a transparency interacting with a placed PDF file results in medium-quality JPEG compressed images

Also, you will need to prepare separated PostScript from QuarkXPress if:

• You want to maintain QuarkXPress traps.
• You are using QuarkXPress 5.x or later and are using TIFF files that are colorized with spot colors and are not using the colorized TIFF XTension. (This is no longer necessary with QuarkXPress 6.x or later DeviceN output.)
• You have placed DCS files and either want to work "fat" or the DCS is vector-based or a format that cannot be merged by Prinergy OPI.
• You are encountering a problem with composite PostScript from QuarkXPress.