From The Art and Popular Culture Encyclopedia
Hurter & Driffield began pioneering work on the light sensitivity of film in 1876 onwards. Their work enabled the first quantitative measure of film speed to be devised.
Early photography in the form of daguerreotypes did not use film at all. Eastman Kodak developed the first flexible photographic film in 1885. This original "film" was coated on paper. The first transparent plastic film was produced in 1889. Before this, glass photographic plates were used, which were far more expensive and cumbersome, albeit also of better quality. The first photographic film was made from highly flammable nitrocellulose with camphor as a plasticizer (celluloid). Beginning in the 1920s, nitrate film was replaced with cellulose acetate or "safety film". This changeover was not completed until 1933 for X-ray films (where its flammability hazard was most acute) and for motion picture film until 1951.