Source : Free On-Line Dictionary of Computing

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://www.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://www.itknowledge.com/)}].
     
        (1999-02-01)