Adobe INDESIGN 2.0 - USING HELP Help Manual page 324

Adobe InDesign Help
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About trapping imported images
Built-in trapping traps images, such as photographs, to text and InDesign graphics.
However, the images must be saved using a purely pixel-based file format that supports
the color requirements of commercial printing. Built-in trapping will trap images saved in
the BMP, GIF, JPEG, PCX, PICT, PNG, PSD (Photoshop), TIFF, and WMF file formats. Of these,
PSD and TIFF are the most appropriate formats for commercial printing jobs; before using
other formats, consult with your prepress service provider.
In file formats that are not purely pixel-based, the nonpixel data will prevent the image
from working properly with built-in trapping. Built-in trapping cannot trap graphics saved
in the AI (Adobe Illustrator), DCS, EPS, Adobe PDF, or PostScript file formats; if you want to
trap these graphics file formats, use Adobe In-RIP Trapping. It's easy to use one of these
formats by mistake. Here's why:
While EPS and PDF images may appear to consist only of pixels, the pixels are actually
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contained inside a layer of PostScript code.
The Desktop Color Separation (DCS) format is based on EPS, so images saved using DCS
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can't be trapped by built-in trapping.
If you're using an Open Prepress Interface (OPI) server, verify that it creates for-position-
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only (FPO) images using TIFF format, not EPS. If the images are TIFF, it may be possible
to use built-in trapping, as long as you don't select any Omit For OPI options at output
time. (Omit For OPI options are located in the Advanced panel of the Print dialog box
when a PostScript printer is targeted.)
Note: The behavior and precision of trapping within an OPI workflow depends on many
factors, such as the downsampling method the OPI server uses to generate FPO images.
For best results, consult with your OPI vendor for information about integrating Adobe
trapping solutions with the vendor's OPI server.
About trapping imported vector graphics
Both Adobe In-RIP Trapping and built-in trapping can trap text and graphics created with
the tools in InDesign. However, built-in trapping doesn't trap placed vector graphics
such as EPS or PDF files. You can use built-in trapping with documents containing vector
graphics in the following cases:
One way to trap Illustrator art is to save the Illustrator file as a TIFF image, and place that
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image into InDesign. Make sure that you specify TIFF resolution and color options that
are appropriate for your print job; see your prepress service provider if you're unsure
about the best settings.
The text, paths, and frames you create in InDesign won't trap correctly if they overlap a
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frame containing a placed graphic that built-in trapping won't trap, such as placed Illus-
trator art. If the placed vector graphic isn't rectangular, try reshaping the placed
graphic's frame closer to the graphic itself, and away from other objects. For example,
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