A phone sensor doesn't do this, so you add the glow afterwards. A good fake puts a soft red-orange ring around only the brightest lights.
How halation happens
Film is a stack of thin, light-sensitive layers on a clear plastic base. These layers are called the emulsion, and they take in most of the light that hits the film. Some lights are very bright, like a street lamp, a neon sign or the sun shining off chrome. With those, enough light gets all the way through the emulsion and into the base.
At the back of the base, some of that light is reflected. Some of it bounces where the base meets the air behind it. Some sources say light also bounces off the camera's pressure plate. The light travels back up through the base at an angle. It enters the emulsion again from behind, a short distance from where it came in. That second exposure is the halo, and the word "halation" comes from "halo".
The light spreads out on its way down and back. So the glow forms a soft ring around the light, instead of sitting on top of it. The light itself has usually gone pure white. What you notice is a warm edge on the dark side of it. Analog.cafe's explainer covers the angles. It says the bounce where the base meets the air counts for more than the pressure plate.
Why halation is red
There are two reasons.
The first reason is the order of the layers. In a colour negative, light meets the blue-sensitive layer first. Next is a yellow filter that stops blue from going further, then the green-sensitive layer. The red-sensitive layer comes last, closest to the base. So light that bounces back off the base reaches the red layer before anything else.
The second reason is which light gets that far. Blue is taken in near the top and blocked by the yellow filter. Green is mostly used up in the middle. So the light that reaches the base and comes back is mostly long-wavelength light, and the layer waiting for it records red. In the print or scan, that extra exposure shows up as a red halo. Very strong lights send enough light back to reach the green layer as well. That's why the inside of a heavy halo looks orange.
Black-and-white film has only one kind of emulsion, so its halation is a plain white glow. You see it most on old photographs of windows and on film with no anti-halation protection.
The anti-halation layer, remjet and CineStill
For most of photography's history, halation was a fault, because it softens detail around bright edges. So film makers build in a layer that takes in the light before it can bounce back.
- Still film uses a dyed or grey base, or an anti-halation layer between the emulsion and the base. The dye is bleached or washed out during processing, so you never see it on the finished negative.
- Motion-picture film has usually used remjet ("removable jet"). Remjet is a carbon-black coating on the back of the base. It takes in stray light and also stops static and scratches. It has to be removed in the ECN-2 process (see Lomography on remjet). Eastman Kodak has said it's replacing remjet on its Vision3 range with an anti-halation layer under the emulsion (Kosmo Foto, 1 June 2025).
Remjet would spoil the C-41 chemicals that ordinary labs use. So CineStill takes Kodak motion-picture film and removes the remjet before selling it, and any lab can develop it. With nothing behind the base, every street lamp gets a red halo. The brand is known for that look. CineStill's own FAQ says the light reflects "inside the film base or off of the pressure plate" onto the red-sensitive layer.
How to fake halation
Many halation filters glow the whole picture or turn the lamp itself pink. A blur of the whole image, blended back in, is a soft-focus or diffusion effect. A white glow is bloom, which comes from the lens or a diffusion filter spreading light of every colour. A flat, strong red looks like a filter. A fake that follows the physics above takes four steps.
- Pick out only the pixels above a high brightness level. Halation comes only from light strong enough to get through the emulsion, so faces and midtones get no halo.
- Blur that layer of bright pixels. Size the blur as a share of the frame's short side. The halo's width depends on how thick the base is, so it shouldn't change with the output resolution.
- Tint the blurred light red-orange, because long wavelengths travel furthest. Real halation fades out as it spreads, because it's a second, weaker exposure.
- Screen the glow back onto the photo. A screen blend makes dark pixels brighter and does almost nothing to pixels that are already white. So the glow lands around the light, and the light stays white.
Do this after the colour look, like grain, since halation belongs to the film stock. If the glow goes on before the film's tone curve, the top of the curve squashes it and shifts its colour. For a black-and-white look, keep the same brightness and leave out the tint.
Dehancer's halation for desktop editors has a brightness threshold and profiles for each film format, with and without remjet. On iPhone, mood.camera's 800T-inspired preset includes halation.
How much halation is too much
A little halation is often enough.
- Look at skin and white clothing. If a white shirt in daylight or a lit face glows red, the threshold is too low.
- Look at the halo's width. It should be a thin edge. If it's wider than the lamp that makes it, make the blur smaller.
- Treat daylight differently. On film without remjet, daylight halation shows mostly where bright sky meets dark branches or rooflines. If a sunny scene looks pink all over, use a fainter halo, or keep a separate look for night.
- Add grain too. A heavy halo on a clean image with no grain looks stuck on. See why digital grain looks fake.
In Chobial
Halation is part of a film's Effects and follows the four steps above. Threshold is the brightness level, from 50% to 100%. Spread sets the blur as a share of the frame's short side. The glow goes on after the film's Strength dial, and in a black-and-white film it has no colour. You see it live in the viewfinder while you shoot.
Each Stock sets Amount, Threshold and Spread, and you adjust them from there:
| Stock | Amount | Threshold | Spread | What it's for |
|---|---|---|---|---|
| Subtle | 18% | 90% | 20% | Still film with its protection. Safe in daylight. |
| Standard | 35% | 82% | 30% | A visible halo on lights at night. A good default. |
| No Remjet | 60% | 72% | 45% | The CineStill-type look. Every lamp and neon sign glows. |
| No Remjet, Heavy | 85% | 62% | 70% | Too much on purpose, for neon, stage lights and night scenes. |
- Open Films (Controls › Film › Manage Films, or Settings). Tap + › New Film and choose a Start From film. Negative is a good base for night colour.
- In Effects › Halation, pick a Stock. Start with Standard.
- Check the preview on a night photo from your library. Hold the preview to compare with how the film started.
- Adjust Threshold until only real lights glow. Then set Spread and Amount.
- Tap the checkmark to save. The film is now in the camera and the editor, so you can develop old night shots again with it.
To change the glow on one photo only, open the photo, tap Edit and choose the Film tool. The Halation slider starts at the film's own amount. Turn it up for a photo full of street lamps, or down for one where the glow gets in the way. The film itself stays the same.
If you'd rather not build one, the Tungsten film already has a glow around the lights. It's modelled on Kodak Vision3 500T, the motion-picture film CineStill 800T starts from. Tungsten has cool colour that leans blue, and quiet greens. Developing and previewing in it are free, and saving in it is Pro. See how the films are made.
CineStill is a trademark of CineStill Film. Kodak and Vision3 are trademarks of Eastman Kodak Company. Chobial is not connected to either company.
