valuebrightness

Valuebrightness is a metric used in color science and digital imaging that combines two common notions of brightness: the value component from the HSV/HSB color models and perceptual luminance. The term is not universally standardized, but it appears in practical workflows as a way to quantify a color’s overall lightness by integrating color channel information with human-perceived brightness.

Definition and components

- Value (V): In HSV/HSB, value represents the brightness of a color as the maximum of its red, green, and blue components. It ranges from 0 (black) to 1 (full intensity).

- Luminance (Y): A perceptual measure of brightness derived from human vision, typically computed from linearized RGB values using a weighted sum that approximates brightness as seen by the eye. Common formulations use Y = 0.2126 R_lin + 0.7152 G_lin + 0.0722 B_lin, where R_lin, G_lin, B_lin are gamma-corrected (linearized) channel values.

Calculation

Valuebrightness combines V and Y through a weighted average: VB = wV * V + wY * Y, with wV + wY = 1 and 0 ≤ VB ≤ 1. A common choice is wV = 0.5 and wY = 0.5, but weights can be adjusted to emphasize either the pure channel brightness (V) or perceptual luminance (Y) depending on the application.

Relation to color spaces

Valuebrightness is related to HSV/HSB and luminance-based metrics used in sRGB, Rec. 709, or other color spaces. It provides a single scalar that reflects both a color’s intensity and its perceptual brightness, aiding tasks such as image enhancement, color grading, accessibility adjustments, and user interface design.

Limitations

As a nonstandardized metric, valuebrightness depends on chosen weights, the method of linearization, and the color space. Results may vary across devices and gamma settings, so consistent calibration is essential for comparative use.