Canon MP-C635 User Manual page 120

A black line will appear on the equalizer corresponding to the area
under the pointer. In this way you can tell exactly where to make your
adjustments.
Setting Tone Curves
ScanTastic provides you with a method of fine-tuning your image with
tone curve settings. These curves operate on the red, green, blue and
master channels of your image. This provides a method of custom image
enhancement.
To work with an individual color channel, click in the box of the
desired color.
N
When the Image Type is set to Gray, only changes made to the Master
channel have any effect.
6-14 Scanning With the MultiPASS C635 Chapter 6