An anti-halation backing
is a layer found in modern photographic films
. It is placed between the light-sensitive emulsion
and the tough film base
, or sometimes on the back of the film base. The light that passes through the emulsion and the base is absorbed by the opaque anti-halation layer. This keeps that light from reflecting off the pressure plate or anything else behind the film and re-exposing the emulsion, reducing contrast. The anti-halation layer is rendered transparent or washed from the film (as in K-14
films) during processing
of the film.