Canon ScanFront 400 Instructions Manual page 93

Front side (Back side) color drop-out
The color drop-out function has a "drop-out" effect that
leaves out a specified color (red, blue, or green) while
scanning, and a "color enhancement" effect that
emphasizes a specified color. You can set each of these
effects for the front side and back side.
IMPORTANT
The color drop-out settings are disabled when the scanning
mode is set to [Color].
Auto Color Detection Settings
This is enabled when Auto Color Detection is selected, and
allows you to configure the following detection settings
for determining whether to scan a document in color or
black and white.
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Chapter 4 Operating Procedures