The Free On-line Dictionary of Computing (30 December 2018):

gamma correction

    Adjustments applied during the display of a digital
   representation of colour on a screen in order to compensate
   for the fact that the Cathode Ray Tubes used in computer
   monitors (and televisions) produce a light intensity which
   is not proportional to the input voltage.  The light
   intensity is actually proportional to the input voltage raised
   to the inverse power of some constant, called gamma.  Its
   value varies from one display to another, but is usually
   around 2.5.

   Because it is more intuitive for the colour components (red,
   green and blue) to be varied linearly in the computer, the
   actual voltages sent to the monitor by the display hardware
   must be adjusted in order to make the colour component
   intensity on the screen proportional to the value stored in
   the computer's display memory.  This process is most easily
   achieved by a dedicated module in the display hardware which
   simply scales the outputs of the display memory before
   sending them to the digital-to-analogue converters.

   More expensive graphics cards and workstations
   (particularly those used for CAD applications) will have a
   gamma correction facility.

   In combination with the "white-point" gamma correction is
   used to achieve precise colour matching.

   Robert Berger's explanation of monitor gamma
   (http://cs.cmu.edu/afs/cs.cmu.edu/user/rwb/www/gamma.html).

   ["Digital Imaging in C and the World Wide Web", W. David
   Schwaderer (http://itknowledge.com/)].

   (1999-02-01)