At a recce you are often given a camera position and a shot to get from it: a medium close-up of the speaker from the back of the room, or a wide of the stage from a balcony. This calculator tells you the focal length that shot needs and whether the lens you plan to bring can do it.
How to use it
Pick the camera format, type the distance from the lens to the subject, and choose a shot size. The shot sizes are set by frame height, so a medium close-up is a frame 0.6 m high at the subject. Type your lens range, and an extender if you use one, to see whether the shot is reachable and the distances at which it is.
The reverse section works the other way. Enter a focal length and it shows the width and height of the frame at that distance, which is useful when a lens is already in the box and you want to know where it can stand.
Where it helps
Use it for choosing between a PTZ and a broadcast camera for a back-of-room position, for checking a long lens will reach a stage from a balcony, and for placing a locked-off camera on a wide. Full-length wide shots on a small PTZ are rarely a problem. Tight shots from far away usually are, and the maths shows it before the load-in.
How it works
Focal length = sensor height x distance / frame height. Distance and frame height must be in the same unit, and the answer is in the unit of the sensor height, millimetres. This is the thin-lens approximation, which is accurate when the subject is much further away than the focal length.
The horizontal angle of view is 2 x arctan(sensor width / (2 x focal length)), and the vertical angle uses the sensor height. Frame width and height at a distance are distance x sensor size / focal length. The angle of view article covers the derivation.
The reach check compares the focal length needed with your lens range, multiplied by the extender. The distance range shown is the range of positions at which the shot falls inside that focal range.
Sensor sizes are 16:9 image areas. The 2/3-inch figure of 9.59 x 5.39 mm is the usual B4 broadcast area. The PTZ, 1-inch, Super 35 and full frame figures are approximate, and the actual area depends on the camera and recording mode, so check the spec sheet. Background on formats is on the image sensor format page.
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Send the client brief and floorplan to Production Office and get back the kit list, signal flow, crew plan and schedule, checked by a broadcast engineer, with nothing of ours on it.