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gamma Gamma is the contrast within the midtones of an image. Increase the gamma and the midtones appear lighter, decrease the gamma and the midtones appear darker. Gamma does not affect either the lightest or darkest values of an image. In other words, lightening up the gamma of an image that has black will not lighten the black nor will darkening the gamma of an image with white darken the white. Since they were originally designed as graphics machines, the default gamma setting for Macintoshes is brighter than that for Windows computers. This allows greater detail and color saturation in the shadows of images, which often results in more accurate color output. However, unless adjustments are made, an image created on a Mac with a gamma of 1.8 when viewed on a PC with a gamma of 2.2 will appear dark, the midrange values losing detail and color depth.
Although
the midtones of the picture above are lighter than those of the
picture below, both contain black and white. Notice the loss of
detail in the shadows.
Histograms
of the Above Pictures
Each histogram is made up of 256 vertical lines representing the
relative strength of each of 256 levels of value. Black is the leftmost
line, while White is the rightmost. Notice how the histogram for
the lighter version of the painting has more and stronger lines
on the right side of the upper graph, while the darker picture has
more and stronger lines on the left of the lower graph.
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