Printing > Trapping > Using trap size guidelines

 

Using trap size guidelines

When considering how to trap your documents, begin by talking to your commercial printer about what needs to be trapped, who is responsible for trapping, and how traps will be created.

Whether you or your print technician apply traps to your document, your print shop should determine the trap width, that is, the amount of overlap for each trap. Differences in paper characteristics, sheet size, screen rulings, and press conditions require different trap widths. The following guidelines illustrate commonly used trap widths for printing on an offset sheet-fed or web press. If you resize a document, you may need to resize the traps.

Trap Size Guidelines

Screen Ruling

(lines per inch)

Trapping Values* (inches)

Trapping Values* (points)

65

0.0077 to 0.0308

0.55 to 2.20

100

0.0050 to 0.0200

0.36 to 1.44

133

0.0038 to 0.0152

0.27 to 1.08

150

0.0033 to 0.0132

0.24 to 0.96

200

0.0025 to 0.0100

0.18 to 0.72


Note: *The lower value assumes excellent press registration when the press is off by no more than half the distance between a row of halftone dots. The higher value assumes less exact press registration when the press is off by a full row of halftone dots.