UMAX Technologies Astra 4000 - Manual (Page 25)

Using the Contrast Bar
This setting controls the difference between light and dark areas in an image. Moving the slider on the
scroll bar to the right increases the gray shades between light and dark areas. Moving it to the left
decreases gray shades between light and dark areas. The default setting is zero (0). The maximum contrast
setting is 100, the minimum setting is –100.
Highlight Bar
This setting defines the lightest (whitest) tones in the scanned image. If you broaden the range that
includes the highlight points, the pixels within the newly specified range to be remapped allowing you to
see more details in a color/gray image.
Moving the slider on the scroll bar to the left increases the brightness. Moving it to the right decreases the
brightness. The default setting is 255. The maximum highlight setting is 255; the minimum setting is 1
(white).
Shadow Bar
The Shadow bar defines the darkest tones in the scanned image. Moving the slider on the scroll bar to the
left increases the brightness in shadowed areas. Moving it to the right decreases the brightness in
shadowed areas. The default setting is zero (0). The maximum shadow setting is 254 (black); the
minimum setting is zero (0).
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 pixels.
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