Logarithmic film speed scale — every 3 DIN points = one stop brighter. European standard now obsolete; replaced by ISO but still found on vintage lenses and literature.
DIN Sensitivity
Those who ordered film in the 70s and 80s ordered by DIN values — 21 DIN for daylight standard, 27 DIN for increased sensitivity, 30 DIN for true low-light work. The logarithmic scale was the European standard, while the Americans had long since switched to ISO. The trick of DIN logic: every three points up meant exactly double the light sensitivity. This seemed cumbersome for quick calculations, but offered more precise gradations for the metric mentality.
In practical work on set, the difference was quickly noticeable. A roll film with 21 DIN still needed a shutter speed of 1/125 in sunlight at aperture 5.6, while the same type with 27 DIN could manage the shot at 1/250. Not much, but crucial for available-light shooting — especially in European studios, where one could rely on the proven DIN code. Cameras had separate DIN rings next to the ISO markings; some DoPs noted both in parallel to avoid errors when changing film.
The transition to the ISO standard in the 90s was less a technical revolution than a political unification. ISO combined DIN and the American ASA — mathematically identical to DIN for most practical values, but a global system. Old light meters and camera exposure calculators with DIN scales slowly fell silent. Nevertheless: those who still work with classic film will find both markings on every can. The DIN value sits to the right of the ISO number — a relic from a time when Europe defended its measurement tradition before standards were homogenized.
Today, DIN is historically relevant and practically dead. Rarely does a camera assistant actively calculate DIN values anymore. However, those who use old exposure tables from Kodak or Fujifilm, or read historical shooting reports, need to know: DIN wasn't wrong, it had just become impractical for international crews. The advantage of logarithmic logic remains theoretically elegant but doesn't compete with global understanding via ISO.