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Term: Gamma

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Term: Gamma

This term has slightly different meanings in conventional photography and in digital imaging; this definition pertains to the latter. The human eye has a nonlinear response curve (it is more sensitive to variations in low light than to equal variation in bright light). In order to present viewers with images that look natural or correct, nonlinear representations are employed. Output devices like display monitors and printers are characterized in terms of their gamma (this can often be adjusted in a calibration step), and professional image-makers process their images (gamma correction) to cater to the output devices they intend to serve and/or to compensate for the inherent tone-reproduction performance of the capture device. Gamma is defined by power-law expressions (see the Wikipedia article on gamma correction) and it is thus a parametric indicator of the level of non-linear light intensity behavior associated with an imaging device. A gamma = 1.0 is generally considered to be linear behavior.
Wikipedia article on gamma correction
Digital Imaging Basics (includes section on gamma)
See also:
Gamma correction