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Gamma
Gamma Correction

(Term of computer graphics)

Most computer and television monitors exhibit a response function that approximates a simple power law, and the exponent is called the monitor's gamma (γ). This means that, given a input signal voltage range between 0 and 100% U for a luminance of 0 - 1, if the monitor receives 50% of that voltage for a specific point, it will display a luminance of L = 0.5*U γ at that point. Typical displays have gamma values between 1.5 and 3.0

The correct display of images, whether computer-generated or captured, requires compensation for the system's gamma response. This gamma correction can be done by the graphics hardware of by software. Some operating systems allready apply a partial correction, bringing the effective system gamma eg. to 1.8 or 1.4.

The Radiance software expects the system variable "DISPLAY_GAMMA" to hold the value of the monitor gamma, so it can apply the appropriate corrections when displaying images. If no system gamma is given, a value of 2.2 is assumed.

 

References:
   luminance
Radiance software
 
 
English    German
gamma    Das Gamma
gamma correction    Die Gammakorrektur
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