What it frames
The Canon EOS 850D with the Canon TS-E 135mm f/4L Macro, over a 30 cm bird on a 1 m fence post. 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.
135mm on the Canon EOS 850D frames 2.48 m × 1.66 m at 15 m: like 216mm on full frame, 9.4° across.
The numbers
- Frame at 15 m2.48 m × 1.66 m
- Full-frame equivalent216mm
- Angle of view9.4° × 6.3°, 11° diagonal
- Depth of field at f/414.2 m to 15.9 m (1.76 m)
- Depth of field at f/813.4 m to 17 m (3.55 m)
- Hyperfocal at f/4255 m
- Hyperfocal at f/8128 m
- 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.