Input Devices, Continued
A scanner allows you to copy a photograph, a drawing, or a text page into
the memory of the computer. It does this by measuring tonal or color values
and converting them into a binary code that the computer can digest. You
may then clean-up the image using the appropriate software program
before printing a final copy for reproduction. Software for the scanner is as
important as the scanner. The software provides for image manipulation and
export format compatibility. A scanner is particularly useful for copying
large amounts of text or images not previously saved on disk that now
require revision. When using a scanner, be careful not to violate an existing
Grey scale scanners read tonal values and assign density code numbers. The
density code is available from 16 to 256 levels of grey. For general-purpose
work, select a software program that offers a minimum of 64 levels of grey.
A color scanner reads color value and assigns it a binary code for export.
This scanner will range from 70 to 600 dots per inch (DPI) with 24 binary
digits (bits) of color. For general-purpose work, select a software program
that offers a range between 300 and 600 dpi.
The four types of scanners are the hand scanner, the flatbed scanner, the
copystand scanner, and the slide scanner.
HAND SCANNERS: Hand scanners are useful for small quantity scanning.
They read portions or excerpts from a document page into the memory of the
FLATBED SCANNERS: Flatbed scanners scan pages out of a book. They
scan an entire one- or two-page spread in one view.
COPYSTAND SCANNERS: Copystand scanners are capable of scanning
SLIDE SCANNERS: Slide scanners scan slides and transparencies into
memory. Scanners used to scan slides and transparencies require a mirrored
or reflective attachment.
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