Adobe 13102498 - Photoshop CS3 - Mac User Manual page 503

Prepare an image with spot channels for printing from another application
If the image is a duotone, convert it to Multichannel color mode.
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2 Save the image in DCS 2.0 format.
In the DCS 2.0 Format dialog box, deselect the Include Halftone Screen and the Include Transfer Function
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options.
Open or import the image in Photoshop, and set your screen angles. Make sure that you've communicated to the
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printer the spot color you want for each of the color plates.
Note: You can place a PSD file containing spot colors directly in Illustrator or InDesign without special preparation.
See also
"Save a file in Photoshop EPS format" on page 454
Change the encoding method
By default, the printer driver transfers binary information to PostScript printers; however, you can choose to transfer
image data using JPEG or ASCII85 encoding. (ASCII85 is a text-encoding method for binary data; it is more
compact than ASCII encoding.) These options are not available for non-PostScript printers, including many inkjet
printers.
Because JPEG-encoded files are smaller than binary files, they take less time to print; however, using JPEG encoding
decreases image quality. Only PostScript Level 2 (or higher) printers support JPEG encoding; if you send a JPEG-
encoded file to a PostScript Level 1 printer, you may get PostScript language errors.
Some print spooler programs, computer networks, and third-party printer drivers don't support binary files or
JPEG-encoded files. Also, some PostScript output devices accept binary and JPEG-encoded image data only through
their AppleTalk and Ethernet ports, not their parallel or serial ports. In these situations, you can select the ASCII85
encoding method. However, ASCII85 files contain about twice as many characters and take twice as long to transfer
as binary files.
Choose File > Print.
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Choose Output from the pop-up menu.
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3 Select an option from the Encoding menu.
Create a color trap
A trap is an overlap that prevents tiny gaps in the printed image caused by a slight misregistration on press. Contact
your service provider before you do any trapping. In most cases, your print shop determines whether trapping is
needed. If so, the print shop staff will tell you what values to enter in the Trap dialog box.
PHOTOSHOP CS3 496
User Guide