Source : Webster's Revised Unabridged Dictionary (1913)

Luminosity \Lu`mi*nos"i*ty\, n.
   The quality or state of being luminous; luminousness.

Source : WordNet®

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