35 mm format
The 35 mm format, or simply 35 mm, is the common name for the 36×24 mm film format or image sensor format used in photography. It has an aspect ratio of 3:2, and a diagonal measurement of approximately 43 mm. It has been employed in countless photographic applications including single-lens reflex (SLR) cameras, rangefinder cameras (film and digital), mirrorless interchangeable-lens digital cameras, digital SLRs, point-and-shoot film cameras, and disposable film cameras.
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The format originated with Oskar Barnack and his introduction of the Leica camera in the 1920s. Thus it is sometimes called the Leica format or Barnack format. The name 35 mm originates with the total width of the 135 film, the perforated cartridge film which was the primary medium of the format prior to the invention of the full frame DSLR. The term 135 format remains in use. In digital photography, the format has come to be known as full frame, FF or FX, the latter invented as a trade mark of Nikon. Historically, the 35 mm format was sometimes called miniature format or small format, terms meant to distinguish it from medium format and large format.