Canon PIXMA MG4200 Series On-Screen Manual page 649

Applies Image Adjustment suitable for photos.
Magazine
Applies Image Adjustment suitable for magazines.
Document
Applies Image Adjustment suitable for text documents.
Important
You can set Image Adjustment after preview.
You can set this setting when Recommended is selected on the Color Settings tab of the
Preferences dialog.
Note
If the image is not adjusted properly with Auto, specify the document type.
The color tone may change from the source image due to the Image Adjustment. In that case, set
Image Adjustment to None.
Reduce Show-through
Use this function to reduce show-through in duplex documents or lighten the base color in recycled paper
and other colored paper when scanning.
OFF
Show-through will not be reduced.
ON
Select this to reduce show-through in duplex documents or lighten the base color. It is
recommended that you normally select this setting.
Important
Reduce Show-through can be set when Recommended is selected on the Color Settings tab of
the Preferences dialog and Document or Magazine is selected for Image Adjustment.
Unsharp Mask
When this is set to ON, the outline of the subjects is emphasized to sharpen the image.
Descreen
Printed photos and pictures are displayed as a collection of fine dots. "Moire" is a phenomenon where
uneven gradation or a stripe pattern appears when such photos or pictures printed with fine dots are
scanned. Descreen is the function for reducing this moire effect.
Note
Even if Descreen is set to ON, some moire effects may remain if Unsharp Mask is set to ON. In
that case, set Unsharp Mask to OFF.
Reduce Dust and Scratches
Scanned photos may contain white dots caused by dust or scratches. Use this function to reduce such
noise.
None
Dust and scratches will not be reduced.
Low
Select this to reduce small dust particles and scratches. Large ones may remain.
Medium
It is recommended that you normally select this setting.
High