Adobe PHOTOSHOP 5.0 User Manual page 53

IMAGE RESOLUTION AND SCREEN FREQUENCY
To ensure high-quality output when printing with
a halftone screen, you need to choose an image
resolution based on the screen frequency of the
printing device. In general, an image resolution
from 1.5 to 2 times the screen frequency gives the
best results.
85 lpi: Average screen
65 lpi: Coarse screen
often used to print
commonly used to
newspapers.
print newsletters and
grocery coupons.
133 lpi: High-quality 177 lpi: Very fine screen
screen typically used typically used for annual
to print four-color reports and images in art
magazines. books.
High-end imagesetters can print at 1200 dpi or
higher and produce good results with images from
200 ppi to 300 ppi.
The number of printer dots or
Screen frequency
halftone cells per inch used to print grayscale
images or color separations. Also known as screen
ruling or line screen, screen frequency is measured
in lines per inch (lpi)—or lines of cells per inch in
a halftone screen.
The relationship between image resolution and
screen frequency determines the quality of detail
in the printed image. To produce a halftone image
of the highest quality, you generally use an image
resolution that is from 1.5 to at most 2 times the
screen frequency. But with some images and
output devices, a lower resolution can produce
good results.
354 ppi (2 x 177 lpi)
A resolution at the low end of the recommended range can
produce good results.
Note: Some imagesetters and 600-dpi laser printers
use screening technologies other than halftoning. If
you are printing an image on a nonhalftone printer,
consult your service provider or your printer
documentation for the recommended image
resolutions.
ADOBE PHOTOSHOP 5.0 45
User Guide
266 ppi (1.5 x 177 lpi)