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S T E P 4
Scanning Techniques
Matching Scan Resolution to Purpose
ScanGear CS-U provides many choices for resolution. What resolution you choose
depends on your output device, how you want to use the image, the type of image,
and your scanner.
In general, it is recommended that you scan the image at a higher resolution than you
need. That way, you retain the amount of information in the image, and if necessary
you can reduce the resolution in the imaging application, after the image has been
scanned and acquired.
Different types of images need different types of scan settings. However, after a certain
point, increases in scan resolution will not improve the output image quality. For
example, a text image can be scanned at 600 dpi for output to a 600 dpi laser printer,
but a color image should be scanned at 180 dpi to be output to a color BJ-printer.
When the image is output to a Bubble jet printer in the color or grayscale mode, for
example, the basic resolution of the printer is halved. For example, for a 360 dpi printer
the basic resolution is set for 180 dpi.
• If your image is black and white with no shades of gray, such as line art, scan
in Black and White mode.
• If you are scanning a text image for conversion into editable text, scan in Text
mode.
• If you are scanning continuous-tone black and white photographs, charcoal
drawings, or any original with shades of gray, scan in Grayscale mode.
• For full-color images, such as photographs or illustrations, scan in Color mode.
• With OCR applications using black and white scan mode, more than 300 dpi is
the recommended scan resolution.
• The minimum scanning width and height will vary according to the selected
scan resolution. For example, at 75 dpi, the minimum size for previewing is 9
pixels per side, which is approximately 0.12 inch or 0.30 centimeter per side.
The minimum at 300 dpi is 35 pixels, which is also approximately 0.12 inch or
0.30 centimeter per side.
Optical and Enhanced Resolutions
Optical resolution refers to the amount of information a scanner can sample per inch.
Different varieties of scanner feature different optical resolutions. The maximum optical
resolution of the CanoScan FB630U or FB636U is 600 dpi for the primary scan
(horizontal dimension of the document) and 1200 dpi for the secondary scan (vertical
dimension).