Adobe Acrobat 7 Professional - Manual (Page 581)

Setting trap widths
Differences in paper characteristics, screen rulings, and printing press conditions require
different amounts of trap. Each Trap Width control allows a maximum value of 8 points.
To determine the appropriate trap widths for each job, consult with your prepress service
provider. Trap presets provide two different settings for trap width (the amount of overlap
for each trap):
●
Default specifies the trap width in points for trapping all colors except those involving
solid black. Enter values from 0p0 to 0p8. The default value is 0p0.25.
●
Black indicates the distance that inks spread into solid black, or the holdback amount--the
distance between black edges and underlying inks for trapping rich blacks. The default
value is 0p0.5. This value is often set to be 1.5 to 2 times the value of the default trap
width. The value you set for Black Color (in the Trap Thresholds section) determines what
Acrobat will consider to be a solid black or a rich black (a process color consisting of
solid black with one or more components of C, M, or Y inks). For details, see
Trapping
with black and rich black .
●
Image specifies the trap width in points for trapping all images. Enter values from 0p0 to
0p8. The default value is 0p0.25.