Camera · Lens & distance
Pick a shot size, then let the tool solve for where the camera goes or which lens to use.
Your apartment is 3 m deep. The actor stands against one wall, your Super 35 camera is against the opposite wall (16:9, horizontal). With the camera body and the actor's own depth, lens-to-actor is 2.7 m. You want a medium shot. What's the longest lens that still fits?
Definitions: shot size = how much of a standing 1.75 m adult fills the frame height. ECU 0.12 m · CU 0.35 m · MCU 0.55 m · MS 0.85 m (waist up) · Cowboy 1.20 m · Full 2.0 m · Wide 4 m · Extreme wide 10 m. Math: distance = focal length × frame height ÷ sensor height (pinhole model, measured from the sensor plane; close-focus breathing ignored). Recorded area: FF 36×20.25, Super 35 24.9×14.0, APS-C 23.5×13.2, MFT 17.3×9.7 mm in 16:9; 2.39 keeps the width. Phone lenses use 35 mm-equivalent focal lengths on a 4:3 frame with a full-frame diagonal, video using the full width; minimum focus distances are typical values.