A color scanner converts photographs, transparencies, and artwork
into an electronic bitmapped image that can be used by the computer.
The bitmap images can be scaled and rotated during the scan. After
the scan, they can be also be scaled (to a minimum) and rotated
or color corrected in an image editing program such as Adobe Photoshop®.
Almost any type of original can be scanned, including photographs,
negatives, transparencies, artwork, previously printed materials,
and text. The text scanning requires an OCR
(optical character recognition) program. Scanners are available
in several different sizes ranging from a small hand-held model
to the large drum scanners. If you need to scan images larger than
the scanner will allow, scan it in pieces and then stitch it together
in an image editing program.
Different types of scanners provide output of different quality
ranging from the low-end, inexpensive scanner, to the high-end,
expensive professional scanner that can cost several thousand dollars.
The low-end scanner may work well for Web, newspaper, and "For
Position Only" (FPO) design/layout images to be replaced later
by a high-resolution scan. The high-end scanners are generally placed
in service bureaus and printing companies where high quality images
are commonly provided.
Note: Any image editing you do
to a FPO image will not automatically be carried over
to the high-resolution image. The changes will also have
to be edited on the high-resolution image.
The key factors for providing high quality scanned images are dynamic
range, resolution, quality of optics, the light source, the number
of bits per color, and aperture.