angular field of view (FOV) or angle of view (AOV)

see also:

• astrophotography

• angular field of view is the viewable scene through your system measured as an angle
• human cone of visual attention is ~55deg which equates to a 43mm focal length lens on a 35mm full frame camera hence lenses with focal lengths in that vicinity are regarded as “standard lenses”

• angle of view in radians = 2 x arctan (d/2f) where d = size of dimension of sensor in mm and f = effective actual focal length in mm
• for telephoto lenses, this approximates to angle of view in degrees = (180/pi) * (d/f)
• effective focal length:
  • for most photography, this is the actual focal length as stated for the lens
  • for macrophotography, the effective focal length = actual focal length x (1+magnification factor), such that for a 1:2 macro, the magnification factor is 1.5
  • for telescopes, effective focal length depends upon whether other elements are used and how they are used such as eyepieces and Barlow lenses
• as an example of subject size, apparent angle of the moon and sun is approx. 0.5 deg

• sensor is 36mm x 24mm and a diagonal of 43.3mm

• sensor size is 17.3 x 13.0mm and a diagonal of 21.63mm = half the diagonal size of a 35mm sensor hence the 2x “crop factor”