What it frames
The Canon EOS R50 V with the Canon RF-S 3.9mm f/3.5 STM Dual Fisheye, over an 8.5 m tree and a 1.75 m person, with hills behind. Everything is drawn to scale: the solid frame is what the camera takes in, the dashed ones are 24, 50 and 135mm on full frame from the same spot. Its APS-C (Canon) sensor (22.3 x 14.9 mm) has a crop factor of 1.6, so the dashed frames are marked with the focal length that gives the same view on it.
3.9mm on the Canon EOS R50 V frames 114 m × 76.4 m at 20 m: like 6.2mm on full frame, 141° across.
The numbers
- Frame at 20 m114 m × 76.4 m
- Full-frame equivalent6.2mm
- Angle of view141° × 125°, 148° diagonal
- Depth of field at f/3.524 cm to infinity (to infinity)
- Depth of field at f/811 cm to infinity (to infinity)
- Hyperfocal at f/3.525 cm
- Hyperfocal at f/811 cm
- Circle of confusion0.018 mm
How it is worked out
The frame at a distance is distance × sensor size ÷ focal length, across and up; the angle of view is 2 × atan(sensor size ÷ (2 × focal length)). Depth of field uses the thin-lens formulas: the hyperfocal distance H = f² ÷ (N × c) + f, the near limit s(H − f) ÷ (H + s − 2f) and the far limit s(H − f) ÷ (H − s), sharp to infinity from H on, with a circle of confusion c of the sensor diagonal ÷ 1500 and, on a zoom whose aperture changes, the maximum aperture taken linearly between its ends. These are for a rectilinear lens; a fisheye takes in more. Ask for this page with Accept: application/json for the numbers alone.