Xerox DocuMate 152i, Scanning Manual

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Image Enhancements TWAIN Scanning Guide
User’s Guide 41
• Threshold —move the slider to the left or right to set the level of lightness or darkness for the
scanner to leverage from.
For example, if you are scanning a document with gray text, such as hand written pencil
notes, move the slider to the right. This tells the scanner that the level to look for is light, and
gray pixels are converted to black pixels instead of white. If the overall tone of the original
document is dark, such as a colored background that may interfere with detecting black,
move the slider left. This tells the scanner that the level to look for is dark, only very dark areas
such as text are converted to black pixels.
If you are scanning documents that are in good condition, with black text on a white
background, the default threshold option will properly scan the item. This level only needs to
be adjusted if the scanned image does not have image clarity similar to the original.
• Sensitivity —move the slider left or right to adjust the sensitivity level for dynamic
thresholding. This slider is only enabled when Dynamic threshold is selected in the list.
Error diffusion, Bayer, and Halftone pattern
Error diffusion, Bayer, and Halftone patterns are the intentional application of noise (dithering) in
the image to help alleviate banding when scanning in binary (black and white) mode. For
example, if you scan a color photo in black and white, the image file will have large blocks of black
and white and the image barely recognizable. Dithering the image creates a black and white
image that is recognizable.
Below is an example of a color scan, a black and white scan without dithering, and a black and
white scan with dithering. When the image is scaled down, it may look like a grayscale scan. When
the image is at normal size or enlarged you will be able to clearly see the dithering pattern, as
shown in the close-up image.
Dither scan - Close up
Color scan
Black and White scan Dither scan