Printing books with conflicting trap presets, Trapping documents and books, About ink trapping – Adobe InDesign CC 2015 User Manual
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Printing
Last updated 6/6/2015
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In the Trap Width section, for Black, enter a distance (in points) for how far you want other colors to spread into
black, or for how far you want support screens choked back under black. Typically, the Black trap width is set to be
1.5 to 2 times the value of the Default trap width.
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For Black Color and Black Density, set values.
Note: To use black trapping features, a color area must use an ink with a neutral density greater than or equal to the Black
Density, and the ink must occur in percentages greater than or equal to the Black Color.
Printing books with conflicting trap presets
You can apply one trap preset to one sheet of output, such as one page. Normally this is not a concern. However, if you
print multiple documents in a book, and each document or page has a different trap preset, InDesign can resolve some
trap preset conflicts by synchronizing presets among documents:
• If documents in a book use different trap presets with the same name, InDesign assigns the trap preset used in the
master document, provided you’ve selected the Trap Preset option in the Synchronize Options dialog box.
• The synchronizing feature makes all the master document’s presets available to the other documents in the book,
but does not assign them; you have to assign trap presets in each document, or use the [Default] trap preset. The
presets appear in the Trap Preset menu of the document’s Assign Trap Presets dialog box.
Note: If different trap presets are applied to pages in a spread, InDesign honors each trap preset.
More Help topics
About InDesign styles and presets
Trapping imported bitmap images
Trapping documents and books
About ink trapping
When an offset printed document uses more than one ink on the same page, each ink must be printed in register
(perfectly aligned) with any other inks that it abuts, so that there is no gap where the different inks meet. However, it’s
impossible to ensure exact registration for every object on every sheet of paper running through a printing press, so
misregistration of inks can occur. Misregistration causes an unintended gap between inks.
You can compensate for misregistration by slightly expanding one object so that it overlaps an object of a different
color—a process known as trapping. By default, placing one ink over another knocks out, or removes, any inks
underneath to prevent unwanted color mixing; but trapping requires that inks overprint, or print on top of each other,
so that at least a partial overlap is achieved.