User`s guide

5-35Reference
To select your resolution unit:
• Choose ppi if your scanned images are
intended for on-screen display; you do not
have to go higher than the target resolution
of your monitor (usually 72 dpi for
Macintosh and 96 dpi for Windows). A
higher resolution will simply increase the
file size of your image without any percep-
tive improvement in image quality.
• Choose lpi if your scanned images are to be
printed. If you choose 1x, for instance, your
scanned image will be printed at 133 lines
per inch, resulting in a 133-dpi image. At
1.5x, the image will be printed at 199.5 dpi;
and at 2x, the image will be printed at 266
dpi. The Custom option allows you to set an
lpi value of your own specification.
In choosing an appropriate lpi value, keep
in mind that if the resolution is too low,
pixelization of the image results, in which
the Postcript language uses a single pixel's
color values to create more than one
halftone dot. If the resolution is too high,
the file size becomes unwieldy and your file
ends up containing more information than
the printer needs, slowing down the printing
process.
Resolution
Resolution is the sampling of image pixel per
measurement unit or the amount of pixel
information stored in an image. Together, the
image resolution and dimensions determine the
file size of the image, which is measured in
kilobytes (KB) or megabytes (MB).
The resolution of an image is important in
determining the quality of the output image.
Resolution is also directly related to file size,
and the higher the resolution, the larger the
resulting file size will be.
When dealing with resolution, remember to
distinguish between optical resolution and
interpolated resolution.
Optical resolution is the "real" resolution as
measured by the scanner's optics. Interpolated
resolution is software-enhanced resolution and
can be useful for enlarging very small images or
for printing line art to obtain superior results.
Resolution Unit
The unit of measurement for resolution is in ppi
(pixels per inch) or lpi (lines per inch). Lpi
settings are dimmed if the ruler unit is in pixels.