Printer Resolution; Screen Frequency - Adobe PHOTOSHOP CS2 User Manual

ADOBE PHOTOSHOP CS2 181
User Guide
20"
15"
832 x 624 / 640 x 480
1024 x 768 / 640 x 480
Example of an image displayed on monitors of various sizes and resolutions
Note: When you are preparing an image for online display, pixel dimensions become especially important. Make sure
that the size of an image allows room for the web browser window controls on smaller monitors.

Printer resolution

Printer resolution is measured by the number of ink dots per inch (dpi) produced by all laser printers, including
imagesetters.
Inkjet printers produce a microscopic spray of ink, not actual dots; however, most inkjet printers have an approx­
imate resolution of 240 to 720 dpi. Many inkjet printer drivers offer simplified print settings for choosing higher
quality printing. To determine your printer's optimal resolution, check your printer documentation.
See also
"About desktop printing" on page 710
"Preparing images for press" on page 718

Screen frequency

Screen frequency is the number of printer dots or 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 higher the resolution of the output device, the finer (higher) a screen ruling
you can use.
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. To determine your printer's screen frequency, check your printer documentation or consult your service
provider.
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.