film grain explained — what it is and why it's used

film grain is the random, sand-like texture you see in images shot on film. it comes from the tiny particles of silver and dye that form the picture, so it's part of the image itself rather than something laid on top of it.

digital cameras don't produce it, which is why it's now often added back on purpose. this guide covers what causes grain, why some film is grainier than others, how it differs from digital noise, and how to add it convincingly.

what causes film grain

film records light with crystals of silver halide suspended in a layer of emulsion. when enough light hits a crystal, development turns it into metallic silver, and those scattered particles are what you see as grain. in black-and-white film the grain is the silver itself. in colour film the silver is removed during processing and replaced by clouds of dye, so the grain is made of those dye clouds instead.

because the crystals are scattered at random, no two frames have the same grain. in motion it shimmers, which is a large part of why film footage feels alive.

why some film is grainier than others

film speed. larger crystals catch light more easily, so fast film uses them. as wikipedia puts it, large crystals give "more sensitive film, for the price of being visibly grainier. fine grain better preserves details but requires more light." an iso 800 stock is grainier than an iso 50 one for the same reason.

format size. grain becomes more noticeable the more a frame is enlarged. a 16mm frame is much smaller than a 35mm frame, so it has to be blown up more to fill the same screen, and its grain is blown up with it. that's why 16mm has a chunkier, more textured look than 35mm.

brightness. grain isn't equally strong everywhere in the picture. the engineers who built grain handling into the av1 video codec model "film grain strength… as a function of intensity", meaning how bright each part of the image is.

film grain vs digital noise

both are random texture, but they aren't the same thing. digital noise comes from the camera sensor, most obviously at high iso. according to a paper from netflix and google engineers, sensor noise "is usually uncorrelated between the samples and has different characteristics from film grain", while film grain is "spatially correlated and grains can be more than one sample in size."

in practice, film grain has clumps with some size to them, while sensor noise is finer and pixel-level. that's why grain added in post can make footage read as film, and simply leaving noise in usually doesn't.

why movies still have film grain

many films are still shot on film, and their grain is part of the image the filmmakers intended. digital films often have grain added deliberately: the same netflix and google paper notes that "digital cameras do not produce film grain; however, in post-production, film grain is often added to the captured material to create the 'movie' look."

grain does practical work too. it hides banding in smooth gradients like skies, and it softens the too-clean look of digital footage.

why grain can look bad on streaming

grain is random, and random detail is exactly what video compression struggles with. the paper puts it simply: "the random nature of film grain is difficult to compress using traditional coding tools." a heavily compressed stream either spends a lot of data on the grain or smears it into blocky mush.

the av1 codec solves this with film grain synthesis: the grain is removed before encoding, a small description of it is sent alongside the video, and your device generates fresh grain during playback. the paper reports bitrate savings of up to 50% on footage with heavy grain, and keeps the grain rather than smearing it away.

film grain in games: on or off?

in games, film grain is a filter the game's renderer adds on top of the picture to make it feel more cinematic. there's no film involved and nothing to preserve, so it's purely a matter of taste. if you find it distracting, switch it off in the graphics settings; if you like the texture, leave it on.

how to add film grain convincingly

good digital grain copies how real grain behaves, not just how it looks in a still.

1. grade first, grain last. add grain after your colour grade, so the grade isn't pushing the grain around.
2. keep it subtle. grain is most convincing when you only notice it once you look for it.
3. match the format. fine grain reads as slow 35mm stock; larger, coarser grain reads as fast film or 16mm.
4. let it vary with brightness. a flat noise overlay sits on top of the image. grain that responds to brightness looks like it belongs to it.

in luttie, grain lives under film effects: amount sets how visible it is and size sets how coarse. luttie's grain is strongest in the midtones and fades out toward pure black and pure white, and it's monochrome, so it adds texture without colour speckle. film effects are part of luttie pro.

one limit to know: grain can't be saved into a lut, because a lut can only change colours, not add texture. it's included when you save an image or video, but if you export your grade as a lut, add the grain in your editing app. why your lut doesn't include vignette or grain explains why.

for the full walkthrough on video, see how to add film grain to video online. grain pairs naturally with halation, the red glow film adds around highlights, and with a film look like portra 400 or kodak 500t. to compare film stocks on your own photo, try the free film simulator.

summary

• film grain is the random texture of the silver or dye that forms a film image
• faster film and smaller formats like 16mm are grainier
• digital noise comes from the sensor and looks finer and more pixel-level than grain
• grain is often added to digital films deliberately, and streaming codecs like av1 regenerate it on playback
• add grain last, keep it subtle, and let it vary with brightness

add grain to your own photo in the editor →