Instant film is a type of photographic film that was introduced by Polaroid Corporation to produce a visible image within minutes or seconds of the photograph's exposure. The film contains the chemicals needed for developing and fixing the photograph, and the camera exposes and initiates the developing process after a photo has been taken. In earlier Polaroid instant cameras the film is pulled through rollers, breaking open a pod containing a reagent that is spread between the exposed negative and receiving positive sheet. This film sandwich develops for some time after which the positive sheet is peeled away from the negative to reveal the developed photo. In 1972, Polaroid introduced integral film, which incorporated timing and receiving layers to automatically develop and fix the photo without any intervention from the photographer. Instant film has been available in sizes from (similar to 135 film) up to size, with the most popular film sizes for consumer snapshots being approximately (the image itself is smaller as it is surrounded by a border). Early instant film was distributed on rolls, but later and current films are supplied in packs of 8 or 10 sheets, and single sheet films for use in large format cameras with a compatible back. Though the quality of integral instant film is not as high as conventional film, peel apart black and white film (and to a lesser extent color film) approached the quality of traditional film types. Instant film was used where it was undesirable to have to wait for a roll of conventional film to be finished and processed, e.g., documenting evidence in law enforcement, in health care and scientific applications, and producing photographs for passports and other identity documents, or simply for snapshots to be seen immediately. Some photographers use instant film for test shots, to see how a subject or setup looks before using conventional film for the final exposure. Instant film is also used by artists to achieve effects that are impossible to accomplish with traditional photography, by manipulating the emulsion during the developing process, or separating the image emulsion from the film base. Instant film has been supplanted for most purposes by digital photography, which allows the result to be viewed immediately on a display screen or printed with dye sublimation, inkjet, or laser home or professional printers. Instant film is notable for having had a wider range of film speeds available than other