Sentence:  As the result of a series of experiments on <WSD>halation</WSD> carried out with backed and unbacked plates, ordinary film and stripping film, Ernest Marriage concludes that there are two varieties of <WSD>halation</WSD>, one due to reflection from the support and the other due to spreading of the light in the film. 
Meaning of the word marked with <WSD> tags:  The blurring of light around a bright area of a photographic image, or on a television screen.