Halation
Halation is the red-orange glow film puts around bright lights when light bounces back through the emulsion. Learn why it's red and how film stocks prevent it.
What is halation?
Halation is a soft glow, usually red or orange, that forms around bright lights and highlights on photographic film. Light passes through the light-sensitive layers, reflects off the back of the film base and comes back up to expose the emulsion a second time, slightly to the side of where it first struck.
The name comes from halo. Kodak's motion picture glossary defines it as a local fog around light sources or sharp highlights, caused by light scattering in the emulsion or reflecting back into it.
Why is halation red?
Color film stacks three sensitive layers. Blue is on top, green in the middle and red at the bottom, closest to the base. Light that bounces back off the base reaches the red layer first and spends most of its energy there before it gets anywhere near the green and blue. So the extra exposure lands mostly in red, and on the final image the halo around a lamp or a car headlight comes out red to orange.
Black-and-white film has the same problem, only the halo is gray. It was worst on fast films with thick emulsions, where light had more room to spread sideways on its way back. In the days of glass plates it was worse, because the thick glass behind the emulsion bounced light back from far away, so photographers shooting interiors with bright windows bought plates with a dark backing painted on.
How film stocks fight it
Modern films carry an antihalation layer, a dark coating that soaks up light before it can return. On most still films it's a dye that washes out in processing. Cinema negative uses a carbon black backing that's softened and scrubbed off at the very start of developing.
That backing would contaminate the chemistry at an ordinary photo lab, so CineStill strips it from Kodak cinema film and sells the result for regular C-41 development. Without it, every street light and neon sign shot on CineStill 800T comes out with a strong red ring.
How to recognize halation
Real halation is tight. It hugs the edge of a bright object, and it's strongest where a bright highlight meets a dark area, such as a lamp against a night sky or a window frame from inside. It tints toward red even when the light source itself is white or blue. A big, colorless haze across the frame is bloom from the lens or a diffusion filter. Digital sensors have no film base to bounce light off, so they don't make halation at all.
Adding halation to digital footage
Bloom Effect can do it with a high Threshold, around 0.8, a low Spread near 0.35 and a red-orange Tint, so only the lights get a halo and it stays close to them. For moving footage that should read as home movies, Super 8 Film Effect adds the grain, flicker and gate weave around it.
Try it
Bloom Effect
Halation and bloom effect for photos and video: bright parts spill soft light into their surroundings, as a red film glow or white haze. Free, in your browser.
Super 8 Film Effect
Super 8 film effect for video and photos: amber faded color, grain, flicker and gate weave that step at 18 frames a second, like an old home movie reel.