What it frames
The OM System PEN with the Voigtländer Nokton 17.5mm f/0.95 Aspherical, over a 1.75 m person in a street, with a door, a parked car and buildings. 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 Micro Four Thirds sensor (17.3 x 13 mm) has a crop factor of 2, so the dashed frames are marked with the focal length that gives the same view on it.
18mm on the OM System PEN frames 4.94 m × 3.71 m at 5 m: like 35mm on full frame, 53° across.
The numbers
- Frame at 5 m4.94 m × 3.71 m
- Full-frame equivalent35mm
- Angle of view53° × 41°, 63° diagonal
- Depth of field at f/0.94.09 m to 6.43 m (2.35 m)
- Depth of field at f/81.74 m to infinity (to infinity)
- Hyperfocal at f/0.922.4 m
- Hyperfocal at f/82.67 m
- Circle of confusion0.014 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.