Avision AV100CS User Manual page 29

Each image type is described as follows:
Line art
Halftone
Gray (256 levels of gray scale)
True Color (16.7 million colors)
256 Colors
Line art includes only black and white areas.
There are no intermediate shades of gray in
between.
Halftone simulates different shades of gray by
varying the threshold value of a matrix.
Scanner recognizes each point in the image as a
shade of gray (continuous tone). 8-bit gray gives
more detailed information about the image.
Color image have continuous tones along with its
color hues.
The 256 colors image provides 256 levels of color
hues.
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