Darkroom Tip: Expired Film: One Stop Per Decade

Film loses effective speed and gains base fog with age. The working rule is one extra stop of exposure for every decade past the expiry date — so a 1990s ISO 400 roll gets metered somewhere around 100–200. Colour film also drifts toward colour casts as its layers age unevenly; black-and-white mostly just fogs and goes flat.

Storage beats arithmetic every time. Film kept frozen or refrigerated since new can shoot at close to box speed decades later, while a roll that spent two summers in a glovebox may be past rescuing no matter how generous you are.

Meter the shadows you actually care about — Analogly's Light Meter spot mode makes that a deliberate choice rather than a hope — and record the ISO you rated each roll at in the Roll Log so the next expired brick benefits from what this one taught you.