The DICT Development Group

  luminance
      n 1: the quality of being luminous; emitting or reflecting
           light; "its luminosity is measured relative to that of our
           sun" [syn: luminosity, brightness, brightness level,
           luminance, luminousness, light]

  brightness
  luminance
  tone
  value
  
      (Or "tone", "luminance", "value", "luminosity",
     "lightness") The coordinate in the HSB colour model that
     determines the total amount of light in the colour.  Zero
     brightness is black and 100% is white, intermediate values are
     "light" or "dark" colours.
  
     The other coordinates are hue and saturation.
  
     (1999-07-05)