In photography, angle of view (AOV)[1] describes the angular extent of a given scene that is imaged by a camera. It is used interchangeably with the more general term field of view.
It is important to distinguish the angle of view from the angle of coverage, which describes the angle range that a lens can image on a given image sensor or film location (the image plane). In other words, the angle of coverage is determined by the lens and the image plane while the angle of view (AOV) is decided by not only them but also the film or image sensor size. The image circle (giving the angle of coverage) produced by a lens on a given image plane is typically large enough to completely cover a film or sensor at the plane, possibly including some vignetting toward the edge. If the angle of coverage of the lens does not fill the sensor, the image circle will be visible, typically with strong vignetting toward the edge, and the effective angle of view will be limited to the angle of coverage.
As abovementioned, a camera's angle of view depends not only on the lens, but also on the image sensor or film. Digital sensors are usually smaller than 35 mm film, and this causes the lens to have a narrower angle of view than with 35 mm film, by a constant factor for each sensor (called the crop factor). In everyday digital cameras, the crop factor can range from around 1, called full frame (professional digital SLRs where the sensor size is similar to the 35 mm film), to 1.6 (consumer SLR), to 2 (Micro Four Thirds ILC), and to 6 (most compact cameras). So, a standard 50 mm lens for 35 mm film photography acts like a 50 mm standard "film" lens on a professional digital SLR (with crop factor = 1) and would act closer to an 80 mm lens (= 1.6 × 50 mm) on many mid-market DSLRs (with crop factor = 1.6). Similarly, the 40-degree angle of view of a standard 50 mm lens on a 35 mm film camera is equivalent to an 80 mm lens on many digital SLRs (again, crop factor = 1.6).