126 film

126 is the number given to a cartridge-based film format used in still photography. It was introduced by Kodak in 1963, and is associated mainly with low-end point-and-shoot cameras, particularly Kodak's own Instamatic series of cameras.

Although 126 was once very popular, as of 2008^[update] it is no longer manufactured, and few photofinishers will process it.

In 1963, Kodak introduced a new film, encased in a plastic cartridge, for which they re-introduced the "126" designation. (The number was originally used for the unrelated 126 roll film format from 1906 to 1949). The term "126" was intended to show that images were 26 mm square, using Kodak's common 1xx film numbering system. However the image size is actually 28×28 mm, but usually reduced to approximately 26.5×26.5 mm by masking during printing or mounting.

The 126 film format was defined in ISO 3029, which has since been withdrawn.

Like the 120 format, there is a continuous backing paper, and the frame number is visible through a small window at the rear of the cartridge. Cameras for this type of film are equipped with a large rectangular window in the back door, through which is visible not only the frame number, but also a portion of the label showing the film type and speed. The cartridge has a captive take-up spool, but no supply spool: the film and backing paper are simply coiled tightly and placed in the supply end of the cartridge. The positioning of the image is fixed by the cartridge. The film is 35 mm wide, but unlike 135 film, it is unperforated, except for one registration hole per image, similar to the earlier 828 film. The camera is equipped with a sensing pin which falls into this hole when the film is fully advanced to the next frame, at which point the winding knob or lever is locked, so as to prevent winding past the pre-exposed frame lines.

The top edge of the cartridge above the film gate has a square notch in a specific position corresponding to the speed of the film in the cartridge. Some of the higher-end cameras used this notch to determine the correct exposure, or to set the light meter, if so equipped. Although only film with speeds between ISO 64/19° and ISO 400/27° were ever manufactured in this format, the standard defined 20 different speeds, from ISO 20/14° to ISO 1600/33°.

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