gammakorrektiot

Gamma correction, also known as gamma encoding or gamma compression, is a non-linear operation used in image processing and video systems to encode and decode luminance or tristimulus values. It is applied to ensure that the brightness of an image appears consistent across different displays and viewing conditions.

The term "gamma" comes from the exponent in the power-law function used to represent this correction: $V_{out} = V_{in}^{\gamma}$. In this equation, $V_{in}$ represents the input intensity value, $V_{out}$ represents the output intensity value, and $\gamma$ is the gamma value. A gamma value of 1.0 represents a linear relationship, meaning the output intensity is directly proportional to the input intensity.

Historically, cathode ray tube (CRT) displays exhibited a non-linear response to the input voltage, where the emitted light intensity was approximately proportional to the input voltage raised to a power, typically around 2.2 to 2.5. This inherent characteristic of CRTs was called their gamma. To compensate for this, images intended for display on CRTs were pre-corrected with an inverse gamma function, so that when the image data was processed by the display's gamma, the resulting image appeared linear and thus displayed correctly.

Modern displays, such as LCD and OLED, do not inherently have this CRT-like gamma response. However, the convention of gamma correction has persisted for compatibility and to ensure consistent visual output. Therefore, images are still typically encoded with a gamma of 2.2 for display on these modern devices. Gamma correction is crucial in photography, video editing, and computer graphics to achieve accurate color reproduction and perceived brightness. Incorrect gamma settings can lead to images appearing too dark or too bright, with loss of detail in shadows or highlights.