How to use it
- Pick metric or US units and a sensor. For a different sensor choose Custom and enter its width and height in millimetres.
- Enter the focal length of your lens in millimetres and the distance to your subject.
- Read the three angles and the width and height of the scene covered at that distance.
How it works
For a sensor dimension d and focal length f, the angle of view is 2 × atan(d ÷ 2f). The width of the scene at distance s follows from similar triangles: s × d ÷ f. The diagonal dimension is √(width² + height²).
Worked example
A 50 mm lens on a 36 × 24 mm full-frame sensor: the horizontal angle is 2 × atan(18 ÷ 50) ≈ 39.6°, the vertical 27.0° and the diagonal 46.8°. At 5 m the frame covers 5 × 36 ÷ 50 = 3.6 m wide and 2.4 m tall.
Tips
- A smaller sensor with the same lens sees a narrower angle, which is why a crop factor multiplies the effective focal length.
- To fit a subject of known width in the frame, rearrange the formula: distance = width × f ÷ sensor width.