What is Gamma?
| Measure Of Contrast In An Image |
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The characteristics of displays using phosphors (as well as some cameras) are nonlinear. A small change in voltage when the voltage level is low produces a change in the output display brightness level; but this same small change in voltage at a high voltage level will not produce the same magnitude of change in the brightness output. This effect, or actually the difference between what you should have and what you actually measured, is known as gamma. Gamma is a measure of contrast in an image, typically in the midrange grays (mid-tones). Many image editing programs express gamma as a curve which can be manipulated by moving points to change the contrast of the image. Adjusting the gamma allows you to correct mid-tones without noticeable changes in the highlight and shadow areas. Gamma is also the way the brightness of an image is interpreted by computer hardware. Many monitors and graphics cards let you adjust the gamma level to alter the monitor appearance or to compensate for brightness or color in a room. This is one reason why the same image may look very different on two different monitors. |
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