Colour Reversal Film
Film that produces a positive transparency directly, viewable and projectable without printing.
Measured in
ISO
In depth
Also called slide or transparency film, it offers saturated colour and fine grain but very narrow latitude — often only a stop and a half in total, with highlights clipping abruptly. That severity made it the professional standard for publication, because what the editor saw on the lightbox was exactly what the photographer had captured.
Examples in practice
A Velvia landscape a half stop overexposed loses its cloud detail permanently, with no negative to print differently.