Avision AVA3 400 - Manual (Page 37)

Scanner Operation
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Halftone
In addition to the black and white display, Halftone simulates
grayscale by using different size of dots. Particularly when you
view the image at a certain distance, it looks very closely like a
gray image yet it consumes the least disk space. Halftone is the
picture that we usually see in newspapers or magazines. Since
Halftone is one type of black and white image, the disk space
required to save a halftone image is 1/24 of that required to
save a 24-bit true color image.
Figure 4-6 Halftone Image