Definitions for halationheɪˈleɪ ʃən, hæ-
Random House Webster's College Dictionary
ha•la•tionheɪˈleɪ ʃən, hæ-(n.)
a blurred effect around the edges of highlight areas in a photographic image.
Origin of halation:
1855–60; hal (o ) + -ation
The action of light surrounding some object as if making a halo.
The blurring of light around a bright area of a photographic image, or on a television screen.
an appearance as of a halo of light, surrounding the edges of dark objects in a photographic picture