UMAX Technologies Astra 2100U - Manual (Page 48)

42
Gamma Bar
The Gamma bar alters the mid-range gray tones in the scanned
image. All optical devices, such as monitors and scanners, have
some variance in their light sensitivity characteristics. To get a
scanned image with good results, VistaScan provides gamma
adjustment capabilities so you can compensate for this variance in
your scanner.
Moving the slider on the scroll bar to the right increases the
brightness of the mid-range gray tones. Moving it to the left
decreases the brightness of the mid-range gray tones. The default
setting is 1.2.
Reset Button
Click the Reset button to cancel the changes and return the value to
the default setting.
Adjusting the Image Tones
The Curve command is another way to make precise adjustments in
the highlight, midtones, or shadow levels in your images. Using
this feature corrects the gray/color values in an image. You change
the values by altering the shape of the curve that represents the
brightness values of pixels.