change in hue produced by changing the luminance (within the range of photopic vision) of a colour stimulus while keeping its chromaticity constant
Note 1 to entry: With certain monochromatic stimuli, hue remains constant over a wide range of luminances (for a given condition of adaptation). The wavelengths of these stimuli are sometimes referred to as "invariant wavelengths".
Note 2 to entry: With increasing intensity, below 510 nm hues shift more towards blue, and above 510 nm hues shift more towards yellow (reds become yellower with increasing brightness).
Note 3 to entry: This entry was numbered 845-02-39 in IEC 60050-845:1987.
Note 4 to entry: This entry was numbered 17-86 in CIE S 017:2011.