Photography Calculators

Sensor & focal length

Field of View Calculator

Field of view is the patch of the subject plane that fills the frame. Width is (subject distance minus focal length) times sensor width over focal length — the thin-lens finite conjugate, not the infinity shortcut. Use it to see whether a 50 mm at 5 m covers a three-person group, or how big a backdrop you need. Subject plane parallel to the sensor.

Inputs

Units
mm

Barrel focal length.

mm
mm
m

Distance from the sensor plane to the subject plane. Imperial shows feet.

Results

Frame width at subject
3.56m
Frame height at subject
2.38m
Frame diagonal at subject
4.28m
Frame area at subject
8.47m²

Recommended gear

Calculation method

Thin-lens magnification is f/(u − f), so framed width is sensor width times (u − f)/f. Height uses sensor height the same way. Diagonal is the hypotenuse of those two sides; area is width times height. A 50 mm on full frame at 5 m covers about 3.56 m × 2.38 m, not the 3.6 m × 2.4 m infinity approximation.

Exact formula

widthM = (u − f) × sensorWidthMm / focalLengthMm with u and f in metres (f = focalLengthMm/1000). Same for height. diagonal = hypot(w,h). area = w×h. Invalid if u ≤ f. Limits: Thin lens, plane parallel to sensor; distortion, camera tilt, pupil shift and focus breathing omitted; the infinity shortcut distance×sensor/f overstates close-up frames.

Lighting the frame

A 1.2 m octabox does not cover a 3.6 m-wide frame evenly. Use the width here to size lights and backdrops before the client arrives.

Drone and mapping

The same similar-triangles math is a camera footprint at altitude. See drone mapping overlap if you are flying a grid.

Frequently asked questions

Is distance to the front of the lens?

Use the sensor plane mark. On a long tele the difference is small; on a 20 mm it is not. Tape from the plane, not the hood.

Group shot rule of thumb?

Give people some headroom. If the calculator says about 3.56 m wide at 5 m, a standing group of four still wants you a step back or a wider lens.

Crop sensor?

Type the real sensor millimetres. Do not also multiply focal length by crop — that would double-count.

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