Plural of halation; optical effects where light reflects inside a camera lens or film, creating blurred halos around bright objects in photographs.
From 'halation' (1891), from the German 'Halo' meaning halo, combined with the English suffix '-ation'. The term was coined to describe the unwanted halo effects photographers observed in early film photography.
Before digital sensors, photographers had to deal with halation constantly—light would bounce off the back of film and create ghostly halos around streetlights in night photos. Camera manufacturers added special anti-halation coatings to film to prevent this, which is why old photographs sometimes look different from what the photographer actually saw.
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