8 mm film

8 mm film is a motion picture film format in which the filmstrip is eight millimeter wide. It exists in two main versions: the original standard 8mm film, also known as regular 8mm or double 8mm, and Super 8. There are also two other varieties of Super 8 which require different cameras but which produce a final film with the same dimensions. The standard 8 mm film format was developed by the Eastman Kodak company during the Great Depression and released on the market in 1932 to create a home movie format that was less expensive than 16 mm. The film spools actually contain a 16 mm film with twice as many perforations along each edge than normal 16 mm film, which is only exposed along half of its width. When the film reaches its end in the takeup spool, the camera is opened and the spools in the camera are flipped and swapped (the design of the spool hole ensures that this happens properly) and the same film is exposed along the side of the film left unexposed on the first loading.... full article at wikipedia