On Angle of View, Focal Length & Crop Factor
Buy a lens today, and its barrel will almost certainly come marked with a focal length. To establish what the angle of view is, though, one would have to either whip out that old scientific calculator for a little trigonometry or, alternatively, locate the manufacturer's detailed specifications.
Angle of View Calculation
Angle of View (AoV) describes the angular extent of a scene captured by a camera. It is represented by the lowercase Greek symbol for alpha – α. The formula for calculating the AoV is written as follows where d = the diagonal dimension of a camera's image sensor and f = the focal length of the lens.