Create a color trap, Determine scan resolution for printing – Adobe Photoshop CC 2014 v.14.xx User Manual
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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.
You can place a PSD file containing spot colors directly in Illustrator or InDesign without special preparation.
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.
Pure cyan and pure magenta spread under each other equally.
1. Choose Edit > Convert To Profile to view the image in the color space of the output device. See Convert document colors to another profile
(Photoshop).
2. Choose Image > Trap.
3. For Width, enter the trapping value provided by your print shop. Then select a unit of measurement, and click OK. Consult your print shop to
determine how much misregistration to expect.
Determine scan resolution for printing
You can use a number of techniques to determine the resolution at which to scan a photograph. If you are scanning photos to be printed, and you
know the exact size and the printing screen frequency, you can use the following techniques to determine the scanning resolution. Often it is
easiest to scan at your scanner's maximum optical resolution and then resize the image in Photoshop later.
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