Epson Expression 1680 - Manual (Page 11)

Optimizing Scanning 1-3
The pointer changes to an eyedropper, with movement
restricted to within the Preview window.
3. Move the eyedropper to the location you want to select as the
highlight point and click it.
The brightness of the pixel at the point you click is set as the
highlight level, and the other parts of the image are adjusted
accordingly.
4. To change the highlight level of the point you selected, move
the Highlight slider left or right, or enter a value between 61
and 490 in the text box.
Making the Shadow setting
Shadows are the darkest areas of an image. Follow these steps to
adjust the Shadow setting.
1. Click the Image Controls button in the Preview window.