This control allows you to apply a gamma correction value to the colors of an image to correct for the difference in gamma levels between the computer's monitor and the equipment that originally produced the image.
Your images may come from many different sources. Some of these sources do not use the same gamma values as your computer's monitor. As a result, your image's colors may not be correct; for instance, the dark areas of your image may be far too dark, but the bright areas may be about correct. This problem can be fixed by applying gamma correction.
An example of an image that may need a gamma correction would be an image that was scanned by a scanner. Scanners use different gamma values than computer monitors.
An example of an image that should not need gamma correction would be an image that was produced with a painting program. Since the colors of the image were selected on a computer monitor, your monitor should be able to represent the original colors.
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