35mm

35mm is a film gauge referring to film stock that is 35 millimeters wide. It has been used for both motion picture film and still photography, and the term describes the formats derived from that stock. In cinema, 35mm has been the dominant gauge since the early 20th century and remains a standard for releases, archival work, and some contemporary productions.

In motion picture practice, 35mm film typically employs perforated stock with four perforations per frame in the common 4-perf system. The image area is about 22 by 16 millimeters, and the original Academy aspect ratio was 1.375:1. Widescreen formats are achieved by masking or cropping the image, and sound can be recorded on the film itself or added via later methods.

For still photography, 35mm refers to the frame size of 24 by 36 millimeters, yielding a 3:2 aspect ratio. 35mm cameras and lenses have been widely used since the mid-20th century, and film speeds are described by ISO (formerly ASA). Color negative and slide films have spanned a range from roughly ISO 50 to ISO 3200, depending on the emulsion.

Today, digital imaging has largely supplanted 35mm film for many applications, but the format remains in use among film enthusiasts and in some professional workflows. Some cinemas continue to project 35mm prints for artistic reasons or archival compatibility, and the aesthetic and archival characteristics of the format continue to influence contemporary imaging.