28mm

28 mm film was introduced by the Pathé Film Company in 1912 under the name Pathé Kok. Geared toward the home market, 28 mm utilized diacetate film stock rather than the flammable nitrate commonly used in 35 mm. The film gauge was deliberately chosen such that it would be uneconomical to slit 35 mm nitrate film.
Pathé in France and later Victor in the United States printed reduction prints (usually, although not always, abridged) of popular films for home rental, designed to be used in Pathéscope Cinematograph or Victor Animatograph projectors.
World War I stopped European production of 28 mm. It continued in North America until 1920 before ceasing entirely. Shortly after, 9.5 mm and 16 mm would take the amateur film gauge role 28 mm had once filled.

View More On Wikipedia.org