Luminance is an objective specification of how illuminated objects appear to an observer.

Luminance is a measurement of the amount of light emitted, passing through or reflected from a surface. Think of a lamp shining in a dark room — luminance describes the amount of light emitted by the lightbulb. 

The subjective experience of luminance is brightness as used by the HSB colour model.

The HSB colour model specifies colours in terms of their Hue (H), Saturation (S) and Brightness (B).

  • Luminance is a measure of the intensity of light or the brightness of a colour that reaches the eye.
  • So we can talk about:
    • The luminance of desert sand under moonlight.
    • The luminance of a road surface under street lights.
    • The luminance of a book cover in sunshine.
  • Luminance can be measured and so is an objective term rather than a subjective experience.
  • The light produced by a table lamp can be described in terms of luminosity. The amount of light that is then reflected from a surface towards an observer can be specified in terms of luminance or described in terms of the brightness of the colour of the surface perceived by an observer.