Angle of view

The angle of view is a function of the focal length of the lens and the dimension of the sensor.

d is the dimension of the sensor in the same rotation as you want to know the angle of view (horizontally, vertically or diagonally but any rotation is possible). Manufacturers specify their lenses using the diagonal angle of view. f is the effective focal length of the lens.

<math>\alpha = 2 \arctan \frac {d} {2 f}</math>

Arctan (Inverse Tangent) can be found as atan or tan^-1 on some calculators.

As an example we calculate the field of view of a 30 mm lens on a Canon 20D that has a horizontal sensor dimension of 22.5 mm.

<math>\alpha = 2 \arctan \frac {22.5} {2 \times 30}</math>

That gives us a horizontal angle of view of 41.1°

• If the result is impossibly small you probably got the result in radians and need to multiply by (180/PI) = 57.296 to get the result in degrees.