Epson Expression 1680 Reference Manual page 14

Click the Tone Correction button in the Preview window, then
select a preset tone curve from the Tone Curve Name list. The
preset tone curves are described below.
Linear
A linear tone curve has no tone correction. Use this setting if you
are satisfied with the tone of the previewed image.
Lighten
Adjusts darker images (like underexposed film) to make them
slightly brighter.
Darken
Adjusts brighter images (like overexposed film) to make them
slightly darker.
Flat Contrast
Flattens high contrast images to make them look more natural.
High Contrast
Increases the contrast of dull images.
Open Shadow
Improves details in the dark areas of images.
Note:
See "Tone Correction" on page 2-40 for more information on tone
correction.
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