Adobe ILLUSTRATOR 6.0, Online Manual, Page: 753 / 893

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The PPD files for high-resolution image-
setters offer a wide range of possible
line-screen rulings paired with various
imagesetter resolutions. The PPD files
for lower resolution printers typically
have only a few choices for line screens,
and they are coarser screens of between
53 lpi and 85 lpi. The coarser screens,
however, give optimum results on lower
resolution printers. Using a finer screen
of 100 lpi, for example, actually
decreases the quality of your image
when a low-resolution printer is used
for final output.
To specify a halftone screen ruling
and resolution:
1
In the Separation Setup dialog box,
choose one of the following options:
• To select one of the preset halftone
screen ruling and printer resolution
combinations, choose one from the
Halftone pop-up menu.
• To specify a custom halftone screen
ruling, enter the lpi value in the
Frequency text box and a screen angle
value in the Angle text box.