Auto Exposure - Epson PERFECTION 1240U Reference Manual

Click the eyedropper button beneath the slider. The mouse
pointer changes to an eyedropper. Then click the color you want
to be gray. The eyedropper "picks up" the color and displays it in
the box beside the eyedropper button. You can then correct the
cast level for that color from 0 to 100 by moving the slider. The
corrected color appears in the box on the right, and the effect
shows up immediately in the preview image. Click Cancel to
restore the original image.
Saturation:
Saturation is the property that defines color depth. Select the
saturation level for color from -100 (less color) to 100 (more color)
by moving the slider.

Auto Exposure

Click the Auto Exposure button on the Manual mode window to
automatically optimize the exposure for an image. The Gamma,
Highlight and Shadow settings in the Image Controls dialog box
are automatically set.
Note:
❏ The Auto Exposure button appears dimmed and is not available
when Pixel Depth is set to Black & White and Auto Area
Segmentation is not selected in the Image Type dialog box.
❏ The Auto Exposure feature is automatically activated when
scanning from the Full Auto mode.
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Understanding EPSON TWAIN Features