halation

plural halations

1. countableuncountableThe action of light surrounding some object as if making a halo.

   1 more example

   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, submerged, as they were, in the fiery glory of the sunset.

   1912, William Hope Hodgson, The Derelict

2. countableuncountableThe blurring of light around a bright area of a photographic image, or on a television screen.

   Halation, properly speaking, is the reflection and diffusion, within the film, from the lighter areas to the adjacent darker ones.

   1917, Photographers' Association of California, Camera craft, volume 24, page 81

   3 more examples

   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.

   1901, E. & H.T. Anthony & Co., Anthony's photographic bulletin for ..., volume 32, page 358

   Among other interesting and weighty opinions, which were in general agreement with our contentions, was one by Mr. H. A. Staddon of Goodmayes, a gentleman who had made a particular hobby of fakes in photography. His report is too long and too technical for inclusion, but, under the various headings of composition, dress, development, density, lighting, poise, texture, plate, atmosphere, focus, halation, he goes very completely into the evidence, coming to the final conclusion that when tried by all these tests the chances are not less than 80 per cent. in favour of authenticity.

   1922, Arthur Conan Doyle, The Coming of the Fairies

   Halation can be prevented or diminished by using an absorbing layer between the sensitive emulsion and the support (anti-halo undercoat) or on the back of the support (anti-halo backing).

   1954, Photography, Theory and Practice, Pitman, page 173