Hue shifts in unrelated and related colours

Abstract Published data on the dependence of hue on luminance (the Bezold‐Brücke effect) is analysed in terms of changes of hue angle instead of changes in wavelength so as to assess their visual importance. For unrelated colours, for a given monochromatic wavelength, the changes in hue caused by altering the luminance vary appreciably according to whether the colours are seen side‐by‐side continuously, or side‐by‐side in flashes, or one‐at‐a‐time in flashes. For related colours, for a given chromaticity, the changes in hue caused by changing the luminance factor are examined in the Munsell and NCS systems; although systematic variations occur, they are different in the two systems, and in neither case is there any similarity to the situation for unrelated colours. Changes in illuminance on related colours do not seem to have any systematic effect on hue for a given chromaticity. It is concluded that the Bezold‐Brücke effect for unrelated colours is not relevant when related colours are considered.