Gamma

Gamma (gamma correction) is the relationship between the numerical value of a pixel stored in an image file (think JPG or TIFF)  and the brightness of that pixel when viewed on-screen.

  • Gamma correction of digital images prevents too much information being stored about highlights that humans cannot differentiate, and too little information about shadows that require more differentiation to maintain the same visual quality.
  • Gamma correction on a digital display is relies on the voltage at each pixel:
    • A computer translates the numerical values in an image file into voltages that are sent to pixels on a monitor. A higher voltage means a brighter pixel.
    • The relationship between stored value and appearance is non-linear, so a change in voltage does not translate directly into an equivalent change in brightness.
    • For many TVs and computer displays, to double the apparent brightness of a pixel might require 2.5 times more voltage. In this case the gamma is said to be 2.5.