Create a color trap – Adobe Photoshop CS4 User Manual
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USING PHOTOSHOP CS4
Printing
Last updated 1/10/2010
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Save a file in Photoshop EPS format
Prepare an image with spot channels for printing from another application
1
If the image is a duotone, convert it to Multichannel color mode.
2
Save the image in DCS 2.0 format.
3
In the DCS 2.0 Format dialog box, deselect the Include Halftone Screen and the Include Transfer Function options.
4
Open or import the image in Photoshop, and set your screen angles. Make sure that you’ve communicated to the
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.
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Save a file in Photoshop EPS format
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.
Trapping to correct misalignment
A. Misregistration with no trap B. Misregistration with trap
Trapping is intended to correct the misalignment of solid colors. In general, you don’t need traps for continuous-tone
images such as photographs. Excessive trapping may produce an outline effect. These problems may not be visible on-
screen and might show up only in print. Photoshop uses standard rules for trapping:
•
All colors spread under black.
•
Lighter colors spread under darker colors.
•
Yellow spreads under cyan, magenta, and black.
A
B