Adobe PHOTOSHOP 5.0 User Manual page 52

44 CHAPTER 3
Getting Images into Photoshop
To determine the image resolution to use, consider
the medium of final distribution for the image. If
you're producing an image for online display, the
image resolution only needs to match the typical
monitor resolution (72 or 96 ppi). However, using
too low a resolution for a printed image results in
pixelation—output with large, coarse-looking
pixels. Using too high a resolution (pixels smaller
than what the output device can produce)
increases the file size and slows the printing of the
image; furthermore, the device will be unable to
print the image at the high resolution. (See
"Screen frequency" on page 45 for guidelines on
choosing an image resolution for a printed image.)
Monitor resolution
displayed per unit of length on the monitor,
usually measured in dots per inch (dpi). Monitor
resolution depends on the size of the monitor plus
its pixel setting. The typical resolution of a PC
monitor is about 96 dpi, of a Mac OS monitor
72 dpi. Understanding monitor resolution helps
explain why the display size of an image on-screen
often differs from its printed size.
The number of pixels or dots
In Photoshop, image pixels are translated directly
into monitor pixels. This means that when the
image resolution is higher than the monitor
resolution, the image appears larger on-screen
than its specified print dimensions. For example,
when you display a 1-inch-by-1-inch, 144-ppi
image on a 72-dpi monitor, it appears in a 2-inch-
by-2-inch area on-screen. Because the monitor
can display only 72 pixels per inch, it needs
2 inches to display the 144 pixels that make up one
edge of the image.
The number of ink dots per inch
Printer resolution
(dpi) produced by an imagesetter or laser printer.
For best results, use an image resolution that is
proportional to, but not the same as, printer
resolution. Most laser printers have output resolu-
tions of 300 dpi to 600 dpi and produce good results
with images from 72 ppi to 150 ppi.