Definition: (1) In photography, a measure of the response of a given film, developer and development regime to light e.g. high gamma indicates high contrast. * Measure of sensitometric contrast obtained from the slope of the straight-line portion of a characteristic curve: although the ordinates of the graph are density and log exposure, gamma is given as a numerical value. * Gamma is 1 where the slope of the straight-line portion is 45º. (2) In monitors, a measure of the correction to the colour signal prior to its projection on screen. * Gamma is the exponent of the transfer function or curve relating video input and output.
Gamma a break
In practice, an increase in the gamma setting of a colour monitor equates with darker screens e.g. a PC screen gamma of 2.2 is darker than the Mac screen of 1.8. Strictly, although gamma is not a measure of contrast: nonetheless, a higher gamma may at the same time have the side effect of increasing contrast in the mid-range brightnesses.

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