Epson Expression 1680 - Manual (Page 13)

Optimizing Scanning 1-5
Making the Gamma setting
Gamma is the difference in contrast between the light tones and
dark tones of an image. Changes in the gamma level only affect
mid-tones, and can be effective for bringing out details normally
hidden in shadow or highlights.
Follow these steps to adjust the Gamma setting.
1. Click the Image Controls button in the Preview window.
2. Move the Gamma slider left or right, or enter a value between
0.5 and 5.0 in the text box.
Applying a preset tone curve
The Tone Correction feature provides preset tone correction
curves that let you adjust the contrast within an image. This gives
you more control over the image when used in conjunction with
the settings in the Image Controls dialog box.