Section 64. About Trapping


64. About Trapping

When a document containing multiple colors is printed, the printing process normally requires several passes , one for each color . If the paper is not perfectly aligned during each pass, colors that should appear touching each other sometimes have gaps between them. This is called misregistration . To compensate for this misregistration, printers employ a process called trapping , where one object slightly overlaps an object of a different color. This slight overlap ensures that, even if the paper is not perfectly aligned during each pass, no gaps appear between colors.

KEY TERMS

Registration Refers to the alignment of the paper during the printing of different colored inks. In a perfectly aligned print job, all the colors print directly on top of each other.

Misregistration The result of poorly aligned printing passes, it causes unwanted gaps between colors.

Trapping A technique used to compensate for misregistration. With trapping, objects are adjusted so they intentionally overlap. This helps avoid the gaps of white space that often appear in misregistered print jobs.


Trapping can be done in either the application in which you created the source document or Acrobat. Acrobat offers numerous ways to set the trapping, including an Ink Manager , the Advanced Print Setup dialog box, and the Document Properties dialog box. However, trapping is not something that the beginning or intermediate Acrobat user should attempt. To quote from Acrobat's own online help:

"Trapping is a complex process that depends on the interaction of various color, ink, and printing factors; the correct settings vary, depending on specific printing conditions. Do not change the default trap settings unless you've consulted with your prepress service provider, and read the trapping topics referred to in the following procedures to make sure that you understand how trapping options work in the context of your specific document and printing conditions."

It is valuable to understand what trapping is and to know that you can set trapping options in Acrobat. Each commercial printer you work with will probably have its own method for trapping that works best for its process and specific printing equipment. Usually, they prefer to do the trapping themselves , or at the very least, they will give you specific instructions on how to set up trapping for your PDF document.



Adobe Acrobat 7 in a Snap
Adobe Acrobat 7 in a Snap
ISBN: 0672327015
EAN: 2147483647
Year: 2005
Pages: 139
Authors: Shari Nakano

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