illumination vs radiance

illumination

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

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

  • Festive decoration of houses or buildings with lights. 

  • Enlightening influence; inspiration. 

  • Splendour; brightness. 

radiance

noun
  • The quality of being radiant, shining, bright or splendid. 

  • The flux of radiation emitted per unit solid angle in a given direction by a unit area of a source. 

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