Adobe PHOTOSHOP 5.0, User Manual, Page: 54 / 400

CHAPTER 3 46
Getting Images into Photoshop
File size The digital size of an image, measured in
kilobytes (K), megabytes (MB), or gigabytes (GB).
File size is proportional to the pixel dimensions of
the image. Images with more pixels may produce
more detail at a given printed size, but they require
more disk space to store and may be slower to
edit and print. For instance, a 1-inch-by-1-inch
200-ppi image contains four times as many pixels
as a 1-inch-by-1-inch 100-ppi image and so has
four times the file size. Image resolution thus
becomes a compromise between image quality
(capturing all the data you need) and file size.
Photoshop supports a maximum file size of 2 GB
and maximum pixel dimensions of 30,000 by
30,000 pixels per image. This restriction places
limits on the print size and resolution available to
an image. For example, an image 100 by 100 inches
can have a resolution of at most 300 ppi (30,000
pixels / 100 inches = 300 ppi).
Changing image size and
resolution
Once you have scanned or imported an image into
Photoshop, you may want to adjust its size or
resolution. The Image Size command lets you
adjust the pixel dimensions, print dimensions, and
resolution of an image.
For assistance with resizing and resampling
images, choose Help > Resize Image. This inter-
active wizard helps you scale your images for printed
or online display.
RESOLUTION, FILE SIZE, AND OUTPUT The file
size of an image refers to the total amount of pixel
information in the image. For example, a 1-inch-by-
2-inch high-resolution image has more pixels, and
thus a larger file size, than a 1-inch-by-2-inch low-
resolution image. In print, a high-resolution image
has more detail than the same image at low resolu-
tion. On-screen, a high-resolution image appears
larger (see page 43). The enlarged on-screen display
does not affect the dimensions of the printed image.
1 in. x 2 in. @ 72 ppi;
file size 323K
100% view on-screen
1 in. x 2 in. @ 300 ppi;
file size 5.47 MB 100% view on-screen