Reddifference

Reddifference, or reddifference, is a term used in color science and image processing to denote a scalar measure of the difference in the red component between two color samples or images. It is not a single standardized metric, but a family of related quantities that isolate the red channel, or the perceived reddening, from other color dimensions.

In its simplest form, reddifference between two samples is the absolute difference of their red channel values, RD = |R1 − R2|, possibly normalized by the maximum red value Rmax to yield a unitless quantity between 0 and 1: RD_norm = |R1 − R2| / Rmax. More robust forms may use squared differences or combine red with weighting to account for luminance or gamma correction.

In imaging applications, reddifference is used to detect color changes due to lighting or processing, highlight red-channel anomalies, or guide color grading.

In vision research, reddifference is used to study how the red channel influences perception or to model red-green color opponency by focusing on red content.

Limitations include sensitivity to white balance and gamma; reddifference does not fully reflect perceptual color difference, and for precise color differences researchers often prefer metrics such as delta E in CIE L*a*b* or CIEDE2000.

Related concepts include red-green difference and other color-difference metrics. See also delta E, color difference, and perceptual color spaces.