Film gauge in the context of "Anamorphic format"

A film format is a technical definition of a set of standard characteristics regarding image capture on photographic film for still images or film stock for filmmaking. It can also apply to projected film, either slides or movies. The primary characteristic of a film format is its size and shape.

In the case of motion picture film, the format sometimes includes audio parameters. Other characteristics usually include the film gauge, pulldown method, lens anamorphosis (or lack thereof), and film gate or projector aperture dimensions, all of which need to be defined for photography as well as projection, as they may differ.

16 mm film is a historically popular and economical gauge of film. 16 mm refers to the width of the film (about 2⁄3 inch); other common film gauges include 8 mm and 35 mm. It is generally used for non-theatrical (e.g., industrial, educational, television) film-making, or for low-budget motion pictures. It also existed as a popular amateur or home movie-making format for several decades, alongside 8 mm film and later Super 8 film. Eastman Kodak released the first 16 mm "outfit" in 1923, consisting of a Ciné-Kodak camera, Kodascope projector, tripod, screen and splicer, for US$335 (equivalent to US$6,182 in 2024). RCA-Victor introduced a 16 mm sound movie projector in 1932, and developed an optical sound-on-film 16 mm camera, released in 1935.

135 film, more popularly referred to as 35 mm film or 35 mm, is a format of photographic film with a film gauge of 35 mm (1.4 in) loaded into a standardized type of magazine (also referred to as a cassette or cartridge) for use in 135 film cameras.

The term 135 was introduced by Kodak in 1934 as a designation for 35 mm film specifically for still photography, perforated with Kodak Standard perforations. It quickly grew in popularity, surpassing 120 film by the late 1960s to become the most popular photographic film size. Despite competition from formats such as 120, 828, 126, 110, and APS, it remains the most popular film size today.

A movie projector (or film projector) is an opto-mechanical device for displaying motion picture film by projecting it onto a screen. Most of the optical and mechanical elements, except for the illumination and sound devices, are present in movie cameras. Modern movie projectors are specially built video projectors (see also digital cinema).

Many projectors are specific to a particular film gauge and not all movie projectors are film projectors since the use of film is required.

35 mm film is a film gauge used in filmmaking, and the film standard. In motion pictures that record on film, 35 mm is the most commonly used gauge. The name of the gauge is not a direct measurement, and refers to the nominal width of the 35 mm format photographic film, which consists of strips 1.377 ± 0.001 inches (34.976 ± 0.025 mm) wide. The standard image exposure length on 35 mm for movies ("single-frame" format) is four perforations per frame along both edges, which results in 16 frames per foot of film.

A variety of largely proprietary gauges were devised for the numerous camera and projection systems being developed independently in the late 19th and early 20th centuries, along with various film feeding systems. This resulted in cameras, projectors, and other equipment having to be calibrated to each gauge. The 35 mm width, originally specified as 1+3⁄8 inches, was introduced around 1890 by William Kennedy Dickson and Thomas Edison, using film stock supplied by George Eastman. Film 35 mm wide with four perforations per frame became accepted as the international standard gauge in 1909, and remained by far the dominant film gauge for image origination and projection until the advent of digital photography and cinematography.

Film perforations, also known as perfs and sprocket holes, are the holes placed in the film stock during manufacturing and used for transporting (by sprockets and claws) and steadying (by pin registration) the film. Films may have different types of perforations depending on film gauge, film format, and intended usage. Perforations are also used as a standard measuring reference within certain camera systems to refer to the size of the frame.

Some formats are referred to in terms of the ratio "perforations per frame/gauge size" to provide an easy way of denoting size. For instance, 35mm Academy is also known as 4 perf-35mm; VistaVision is 8 perf-35mm; the long-time standard Todd-AO 70 mm film is 5 perf-70mm; and IMAX is 15 perf-70mm. This description does not indicate whether the film transport is horizontal or vertical, but uncertainty is precluded because there are currently no horizontal systems using the same number of perforations on the same gauge as a vertical one.