Samsung SF-4500 User Manual page 184

Shadow Control
The Shadow value represents the darkest value in an image. All pixels
below this point will be rendered as pure black. If you subsequently
broaden the shadow points on the Level Adjustment graph, the pixels will
be remapped within the new range thus allowing you to see more detail in
image.
The default value for Shadow is 0, this is the maximum range of darkness
level allowed within any given image. You can increase or decrease the
shadows in a particular image as needed by adjusting this scroll bar.
Scanner Gamma Control
All optical devices such as monitors and scanners have some non-linearities
in their light sensitivity characteristics. MyScan provides Gamma
adjustment for you to compensate for these non-linearities in your scanner,
and produce better scanned images.
To change the gamma value, simply move the Slider to the left or right to
change the values in the adjacent text boxes. The value in the adjacent box
will change in the range 0.1 to 10.0 as the slider moves.
Ordinarily, good results can be obtained from your machine by leaving the
slider at its default value of 1.00.
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