Anti-halation backing
An anti-halation backing is a light-absorbing layer on the back of many photographic films, including most movie films. It sits behind the light-sensitive layer and soaks up light that passes through the emulsion, preventing it from bouncing back and creating halos around bright areas.
In motion pictures, the film sits against a reflective pressure plate, so the backing helps reduce reflections. Still photography film gates are often treated to minimize reflections, so anti-halation backings are less common there. Kodachrome used a backing to protect a very sensitive inner layer.
The backing is removed during processing for color films (for Kodachrome’s K-14 process and for ECN2 color negative film), so it doesn’t stay in the final image.
If the backing is not used, reflections and halo effects can be stronger. Some infrared films, like Kodak HIE, showed a glowing look when they lacked an anti-halation layer.
Even with anti-halation, some films still show a faint red halo around very bright areas because some light is not fully absorbed and scatters into the red layer before being absorbed.
Halation is a feature of analog film and isn’t part of digital footage unless added in post-production.
This page was last edited on 2 February 2026, at 23:46 (CET).