Film Grain

The image carries a texture that changes every frame. It sits between the viewer and the scene, and it is one of the strongest signals that footage was photographed on film.

Grain also hides things. It breaks up banding in a gradient and softens the plastic look of a clean digital image, which is why it gets added long after anyone has stopped shooting on film.

Film records light with silver halide crystals scattered at random through the emulsion. The crystals land differently on every frame, so the texture moves even when nothing in the scene does.

Faster stock has larger crystals, so it is grainier. A 500 speed stock pushed in the dark shows far more texture than a 50 speed stock in daylight, and the difference reads as available light against controlled light.

The texture is not even across the picture. It reads most in the darker mid tones and the shadows, and least in a bright even highlight, which is why the entry asks for it heaviest in the shadows.

Use it on anything meant to read as film, on footage that looks too clean, and over gradients where digital banding would otherwise show.

Leave it off work that has to survive heavy compression. Grain is the hardest thing in a frame for a codec to carry, and it turns to mush at low bitrates.

Halation is a glow spreading out of bright areas, and it lives only around highlights. Film grain is a texture spread across the entire image, and it has nothing to do with where the bright parts are.

The two arrive together on real stock, which is why they get confused. The test is whether the artefact has an edge to hug. Halation does, grain does not.

The texture comes back frozen, identical on every frame, which reads as a dirty sensor rather than as film. Say the grain moves frame to frame.

The second failure is grain laid evenly over everything including the highlights. Ask for it to sit heaviest in the shadows and to thin out in the bright areas.