輝度（ルミナンス）

Luminance is a physical measurement expressed in candelas per square meter (cd/m2 or nits). It quantifies how bright a surface appears to the human eye and is fundamental to display technology, where typical monitors range from 250-400 nits and HDR displays can exceed 1000 nits. In color science, luminance is related to but distinct from lightness, which is a perceptual quality. The Y component of the CIE XYZ color space directly represents relative luminance, forming the basis for all photometric calculations in color science.