Luminance

The term luminance is used when talking about how illuminated objects appear to an observer.

• Luminance is a measure of the intensity of light that reaches the eye.
• So we can talk about:
  • The luminance 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 then be measured in terms of luminance.

https://en.wikipedia.org/wiki/Luminance