halation

noun halations

1. countable, uncountable The action of light surrounding some object as if making a halo. She was, as you know, to the west-ward of us, and the sunset was making a great flame of red light to the back of her, so that she showed a little blurred and indistinct by reason of the halation of the light, which almost defeated the eye in any attempt to see her rotting spars and standing rigging
2. countable, uncountable The blurring of light around a bright area of a photographic image, or on a television screen. As the result of a series of experiments on halation carried out with backed and unbacked plates, ordinary film and stripping film, Ernest Marriage concludes that there are two varieties of halation, one due to reflection from the support and the other due to spreading of the light in the film.

Similar: overglow