Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the crystals determine the sensitivity, contrast, and resolution of the film.

 
The earliest practical photographic process was the daguerreotype; it was introduced in 1839 and did not use film. The light-sensitive chemicals were formed on the surface of a silver-plated copper sheet. The calotype process produced paper negatives. Beginning in the 1850s, thin glass plates coated with photographic emulsion became the standard material for use in the camera.

Although fragile and relatively heavy, the glass used for photographic plates was of better optical quality than early transparent plastics and was, at first, less expensive. Glass plates continued to be used long after the introduction of film and were used for astrophotography and electron micrography until the early 2000s when digital recording methods supplanted them. Ilford continues to manufacture glass plates for special scientific applications.