Canon MultiPASS C50 Software User's Manual page 110

2. To adjust the tone of a particular colour, select the colour from the
Channel list box. Otherwise, leave the channel set to Master.
3. To automatically compensate for common problems in an image,
choose one of the options from the list.
Using a Custom Tone Curve
If you want to experiment with tones, you can create a custom tone curve.
An effective way to create a custom tone curve is first to adjust the preview
image with an appropriate predefined tone curve and then edit the results.
Editing a tone curve involves adding handles to an existing tone curve
and dragging them to change tonal levels in the image. When you drag a
handle to a white area, the shape of the curve changes, and the tones of the
preview image are adjusted.
All handles on the tone curve, including the end points, can be dragged
anywhere within the tone graph. A handle that is dragged outside the tone
graph is deleted; and the tone curve automatically conforms to the
remaining points. Except for the end points, all handles can be deleted.
Chapter 6 Scanning 6-27