Photography Calculators

Sensor & focal length

Field of View Calculator: Sony A7 IV + Sigma 85mm f/1.4 DG DN Art

This page is pre-filled for the Sony A7 IV + Sigma 85mm f/1.4 DG DN Art (Full Frame, 33 MP, 85 mm at f/1.4). Change subject distance to see how many metres of scene sit in the frame.

Group-sized field on the Sony A7 IV + Sigma 85mm f/1.4 DG DN Art

At 5 m the 85 mm on Full Frame covers 2.04 × 1.36 m (2.77 m²). A three-person standing group at 5 m fits; check backdrop width before you hire the studio.

The Result is indicative and educational. It does not constitute a design, a technical opinion or medical advice and does not replace calculations or verification by a person with the appropriate qualifications and authorisations. Before purchase, installation or use in practice – in particular in electrical installations – the Result should be verified by a qualified specialist. Details: Terms of Service, point 4.

Inputs

Units
mm

Barrel focal length.

mm

Active sensor width in millimetres.

mm

Active sensor height in millimetres.

m

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

Results

Frame width at subject
2.04m

Frame width at the subject plane.

Frame height at subject
1.36m

Frame height at the subject plane.

Frame diagonal at subject
2.45m

Corner-to-corner size of the frame at the subject.

Frame area at subject
2.77m²

Width × height at the subject, in square metres.

The Result is indicative and educational. It does not constitute a design, a technical opinion or medical advice and does not replace calculations or verification by a person with the appropriate qualifications and authorisations. Before purchase, installation or use in practice – in particular in electrical installations – the Result should be verified by a qualified specialist. Details: Terms of Service, point 4.

Example products

Product links are Affiliate Links to Amazon websites. Using them does not cost you anything extra, and if you make a purchase we may receive a commission. Details: Terms of Service, point 5.

Calculation method

You measure the distance D from the sensor plane; the lens sits in between, so the lens-to-subject distance is u = (D + √(D(D − 4f)))/2. 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 3.53 m × 2.35 m, not the 3.6 m × 2.4 m infinity approximation; at 4f (0.2 m for a 50 mm) the frame is the sensor itself, 1:1.

Exact formula

u = (D + √(D(D − 4f)))/2 for the sensor-plane distance D. 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 D < 4f. 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 3.53 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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