Nikon FX format

The term full frame is used by users of digital single-lens reflex cameras (DSLRs) as a shorthand for an image sensor format which is the same size as 35mm format (36 mm × 24 mm) film. Historically, 35mm was considered a small film format compared with medium format, large format and even larger. This is in contrast to cameras with smaller sensors (for instance, those with a size equivalent to APS-C-size film), much smaller than a full 35mm frame. Currently, the majority of digital cameras, both compact and SLR models, use a smaller-than-35 mm frame, as it is easier and cheaper to manufacture imaging sensors at a smaller size. Historically, the earliest digital SLR models, such as the Nikon NASA F4 or Kodak DCS 100, also used a smaller sensor. Kodak states that 35mm film has the equivalent of 6,000 pixel horizontal resolution according to a Senior Vice President of IMAX.

If the lens mounts are compatible, many lenses, including manual-focus models, designed for 35mm cameras can be mounted on DSLR cameras. When a lens designed for a full-frame camera, whether film or digital, is mounted on a DSLR with a smaller sensor size, only the center of the lens' image circle is captured. The edges are cropped off, which is equivalent to zooming in on the center section of the imaging area. The ratio of the size of the full-frame 35mm format to the size of the smaller format is known as the "crop factor" or "focal-length multiplier", and is typically in the range 1.3–2.0 for non-full-frame digital SLRs.

When used with lenses designed for full frame film or digital cameras full-frame DSLRs offer a number of advantages compared to their smaller-sensor counterparts. One advantage is that wide-angle lenses designed for full-frame 35mm retain that same wide angle of view. On smaller-sensor DSLRs, wide-angle lenses have smaller angles of view equivalent to those of longer-focal-length lenses on 35mm film cameras. For example, a 24 mm lens on a camera with a crop factor of 1.5 has a 62° diagonal angle of view, the same as that of a 36 mm lens on a 35mm film camera. On a full-frame digital camera, the 24 mm lens has the same 84° angle of view as it would on a 35mm film camera.

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