Film perforations in the context of "70 mm film"

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.

Negative pulldown is the manner in which an image is exposed on a film stock, described by the number of film perforations spanned by an individual frame. It can also describe whether the image captured on the negative is oriented horizontally or vertically. Changing the number of exposed perforations allows a cinematographer to change both the aspect ratio of the image and the size of the area on the film stock that the image occupies (which affects image clarity).

The most common negative pulldowns for 35 mm film are 4-perf and 3-perf, the latter of which is usually used in conjunction with Super 35. 2-perf, used in Techniscope in the 1960s, is enjoying a slight resurgence due to the birth of digital intermediate techniques eliminating the need for optical lab work. Vertical pulldown is overwhelmingly the dominant axis of motion in cinematography, although horizontal pulldown is used in IMAX, VistaVision, and in 35 mm consumer and professional still cameras.

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.

Techniscope or 2-perf is a 35 mm motion picture camera film format introduced by Technicolor Italia in 1960. The Techniscope format uses a two film-perforation negative pulldown per frame, instead of the standard four-perforation frame usually exposed in 35 mm film photography. Techniscope's 2.33:1 aspect ratio is easily enlarged to the 2.39:1 widescreen ratio, because it uses half the amount of 35 mm film stock and standard spherical lenses. Thus, Techniscope release prints are made by anamorphosing, enlarging each frame vertically by a factor of two.