What is Photographic film?
[[Image:undeveloped film.png|thumb|350px|right|Undeveloped Arista black and white film, [[Film speed|ISO]] 125/22°.]] '''Photographic film''' is a sheet of [[plastic]] for recording visual [[scene]]s. The plastic has been coated with an [[emulsion]] that is [[sensitive]] to [[light]]. The image is recorded on the emulsion when it is exposed to light. Film is kept in small canisters (boxes) which protect it from the light. A normal photographic film may hold up to 40 pictures. Once all pictures have been recorded, the film has to undergo a special [[chemical]] treatment. This is called ''developing a film'' or [[film processing]]. That treatment makes the pictures visible (you can see them), and the exposed film is no longer sensitive to light.<ref>Anchell, Steve 2008. ''The Darkroom Cookbook'' p.103-105. Elsevier, Oxford. ISBN 978-0-240-81055-3</ref> Different kinds of films exist. Some require more light to be exposed than others. Some are black and white only; they record no colors. There are also special films which can record [[infrared]] light. Photographic film was invented in the 1880s and replaced the earlier [[dry plate]] system. Films also come in different sizes. 35 millimeter film, the most used size, comes in metal cans or canisters, but there are other camera films that come in paper wrappings or in single sheets. ==Uses== Film can only be used once. After that, it cannot be used again (if it is accidentally used again, this results in an artifact called a [[multiple exposure]]). When not in use, film needs to be covered from light, otherwise it will record any lights that shine on it. This will make it useless to record a picture. Film comes in a can called a [[canister]] to cover it from light rays. Film needs the right amount of light to make a picture. If the picture is too bright or too dark, it will not [[record]] correctly. The longer that the film keeps recording, the more light it will get. If what is being photographed is bright, it will be recorded faster. If it is darker, the