Epson Perfection 640U Reference Manual page 56

Click the Image Controls button on the Manual mode window
to view the following dialog box.
Note:
❏ The Image Controls settings are optimized automatically when you
scan without previewing.
❏ The Image Controls button appears dimmed and is not available
when ICM or ColorSync is selected in the Configuration dialog
box.
❏ If Image Type is set to Text/Line Art, all the settings except
Threshold appear dimmed and cannot be selected.
❏ You can see the effects of the Image Controls settings in the Preview
window.
Exposure:
The Exposure setting lightens or darkens an image. You can select
from -10 (darkest) to 20 (brightest) by moving the slider.
The Exposure and Highlight controls are related. When the
Exposure setting is changed, the Highlight value is automatically
set.
3-10
Understanding EPSON TWAIN Features