Epson PERFECTION 1240U Reference Manual page 68

This setting is useful when scanning color photo.
Color Document:
24-bit Color and best quality with de-screening to remove moiré
patterns
This setting is useful when scanning magazines or catalog in
color.
Note:
A moiré is a cross-hatch pattern that appears on scanned images when
scanning printed material. It is a result of interference that occurs due
to the difference between the pitches of the scanning and the halftone
screens.
Black & White Photo(14-bit):
14-bit gray, best quality
This setting is useful when scanning positive or negative film for
further editing.
Black & White Photo:
8-bit gray, best quality
This setting is useful when scanning black and white photo.
Black & White Document:
8-bit gray, best quality with de-screening to remove moiré
patterns
This setting is useful when scanning magazines or catalog in
monochrome.
Illustration:
24-bit color, best quality with color smoothing
3-8
Understanding EPSON TWAIN Features