Film

Photographic film, generally also known as film is a material needed in photography to get pictures. Film is a plastic sheet coated with a light sensitive material. The light sensitive material is an emulsion with silver halide salts with variable size salt crystals. The different sizes of the crystal are responsible for the sensitivity, resolution and contrast of a film.

Is the film exposed to light a invisible image is created, also called latent image. With several chemical processes applied to the film a visible image is developed.

Black and white films have one layer of salts, while color film usually uses at least three layers.
On a typical color film sheet a blue sensitive layer is on top and a green and red sensitive layer come next.
Through newer technologies companies like Kodak are able to produce film material with 12 Layers (Kodakcolor II).

Photographic film is divided into two categories, print film and color reversal film. Print film when used in cameras produces a negative, an inverted color picture. To develop this film type it needs to be projected through a lens or contacted with the film paper to get the proper positive picture. This kind of film material comes in two color versions, black & white and color.

Color reversal film produces a transparency after being developed. These transparencies can be viewed with a projector. They are also called slide and the film material is often referred to as “slide film”
Regular pictures can be produced from slides, but the process is expensive and more difficult than for print film. Black and White reversal film exists but is very rarely used.

Common film sizes available are 135 or also known as 35mm, APS (Advanced Photo System), 110, 126, 127, 120/220 (medium format film), sheet film in various sizes (large format film) and also motion picture films (like 8mm, 16mm, 35mm and 70mm).

Other special film materials on the market are for example instant film. Instant film has an automated development integrated in the film sheet. The development of the picture is carried out immediately after the exposure of the material.
Other specialty films include films designed to take pictures of Ultraviolet and Infrared light. To be able to shoot either one of the two special lenses and filters are necessary additionally to the specialized film material. Other specialized films include also X-ray and Gamma Ray sensitive film, widely used in medical applications.

Digital photography is drastically reduced the amount of film used. Besides for disposable cameras film is slowly disappearing from the western market.

Film also refers to movie and motion pictures since film material is the most used material to capture films.