Xerox DocuMate 3125 User Manual page 146

Scanning from TWAIN and WIA
Threshold and Dynamic threshold
Threshold enables you to set what level of light or dark to look for on a page. When scanning in
black and white, everything on the page is set to either white pixels or black pixels in the final
image. If the text on the page is a light color, then the text may be gone in the final image as
the scanner will change those light colors to white pixels. The threshold slider lets you set the
level of darkness or lightness of the text on the page. Dynamic threshold attempts to evaluate
the image and dynamically adjust the threshold level. These options work best for documents
that contain only text such as business letters, spreadsheets, reports, etc...
• 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.
Color scan
User's Guide
Black and White scan
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Xerox DocuMate
Bayer dither scan
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3125
7-138