3. Substandard cinema formats

At the same time as the development of professional cinema (silent and sound), small-format amateur and educational cinema began to flourish. The public's interest in popularizing cinematographic practice generated new competition, all the more so as two essential characteristics for their development applied to reduced formats: the non-flammability of the support (known as "safety support") and the invertibility of the emulsions (film whose emulsion makes it possible to directly obtain a positive black-and-white or color image after a shooting operation, followed by development "by inversion") [33] . Small-format cinema has proved a powerful means of information, documentation and education, through the production and distribution of documentary and educational films, teaching films, demonstration films, reports, regional...