Expired film

An emulsion decays. Background radiation and heat expose the silver a little at a time, so the film gains base fog, and that fog lifts the shadows off black. The film also loses speed as it goes, roughly one stop for every decade past the date.

On a colour stock the three layers do not decay at the same rate. One fades faster than the others, so the colour balance drifts, the contrast drops, the grain grows coarse and blotches and streaks appear wherever the decay ran unevenly.

Say how far past the date the film is. A number does far more than the word expired. Ten years, twenty years and forty years are three different amounts of damage, and the model treats them differently.

Name the three effects together. Contrast is low, because the fog fills the shadows with grey. The grain is coarse and uneven. The colour has shifted, usually toward green, magenta or yellow, and it does not shift by the same amount across the whole frame.

Add the marks that only age makes: blotches in the flat areas, streaks along one edge of the frame, and a stain where the backing paper pressed against the emulsion on a roll film. Say heat made all of it worse and faster.

Use it for a picture that should look found rather than taken: an old holiday, a house clearance, a memory, a document with nobody's name on it.

Leave it alone when the colour has to be right. Expired film moves every hue, and it moves them by an amount that nobody chose.

Film soup is deliberate damage done in an afternoon. Expired film is accidental damage done over decades. A soup leaves melted patches and crystalline edges. Age leaves fog, drift and blotches, and it leaves the picture whole underneath them.

Cinema publishes Vintage as its own entry at /techniques/cinema/. That entry is a period look, chosen on purpose and kept tidy. This one is a chemical failure, and the marks land where they land.

Harman Phoenix is a new stock with coarse grain and odd colour by design. It looks unruly and it repeats, roll after roll. An expired roll repeats nothing.

Expired stock became a market of its own after 2005, when digital cameras emptied the shelves and freezers full of 1980s and 1990s film reached the auction sites. Kodak's own withdrawals put more of it there, Kodachrome 64 among them in 2009. A camera bought at a house clearance gives the same thing for nothing: fogged, shifted frames from a holiday that nobody now remembers.

The model returns a clean picture with a yellow filter over it. Say the base fog lifts the shadows to grey, and say the colour shift is uneven across the frame.

The other failure is tidy damage, spread evenly like a border. Ask for blotches in the flat areas and streaks along one edge only.