Gamma
An exponent defining the nonlinear relationship between input signal values and output luminance. Gamma correction ensures natural brightness perception on displays.
Gamma refers to the power-law exponent that describes the nonlinear relationship between encoded pixel values and the actual luminance produced by a display. CRT monitors naturally exhibited a response curve where output brightness was proportional to input voltage raised to approximately the 2.2 power. Gamma correction was introduced to compensate for this characteristic and ensure images appear as intended.
- Gamma encoding: Cameras and scanners apply a gamma curve (for example 1/2.2 ≈ 0.45) to linear light data before storage. This allocates more digital values to darker tones, where human vision is more sensitive to changes
- sRGB standard: The web-standard sRGB color space assumes a display gamma of approximately 2.2. ICC profiles embedded in image files and the PNG
gAMAchunk communicate gamma information to rendering software - Linear workflow: 3D rendering and compositing operations perform calculations in linear (gamma 1.0) space for physically accurate lighting, applying gamma correction only at final output
In image editing, gamma adjustment corresponds to raising or lowering the midtones on a tone curve.