brightness vs illumination

brightness

noun
  • The quality of being bright. 

  • Intelligence, cleverness. 

  • The perceived luminance of an object. 

illumination

noun
  • Splendour; brightness. 

  • Adornment of books and manuscripts with colored illustrations. See illuminate (transitive verb). 

  • Festive decoration of houses or buildings with lights. 

  • Enlightening influence; inspiration. 

  • The act of illuminating, or supplying with light; the state of being illuminated. 

How often have the words brightness and illumination occurred in a corpus of books? (source: Google Ngram Viewer )