The Collaborative International Dictionary of English v.0.48:

Solarization \So`lar*i*za"tion\, n. (Photog.)
   Injury of a photographic picture caused by exposing it for
   too long a time to the sun's light in the camera; burning;
   excessive insolation.
   [1913 Webster]

WordNet (r) 3.0 (2006):

solarization
    n 1: exposure to the rays of the sun [syn: solarization,
         solarisation]