gammakäyrä

Gammakäyrä, often translated as gamma curve or gamma correction, is a nonlinear operation used in image processing and video systems to encode and decode luminance or color values. It represents the relationship between the numerical value of a pixel and its actual brightness. The term "gamma" comes from the exponent used in the power-law function that describes this relationship: output = input ^ gamma.

In many imaging systems, especially older CRT displays, the relationship between the electrical signal and the emitted light was not linear. Displaying an image with a linear signal would result in a darker-than-intended appearance. Gamma correction is applied to compensate for this. When encoding an image, the gamma value is typically greater than 1, compressing the darker tones and expanding the brighter ones. When displaying the image on a gamma-corrected device, the inverse operation (with a gamma value less than 1) is applied to restore the original linear relationship.

The standard gamma value for many systems, like sRGB used on the web and many computer displays, is approximately 2.2. However, the exact gamma value can vary depending on the display technology and the intended application. Understanding gamma is crucial for accurate color reproduction and ensuring that images appear as intended across different devices and platforms. Deviations from the correct gamma can lead to images appearing washed out or overly dark.