What it frames

The OM System PEN with the TTArtisan 40mm f/2.8 Macro, over a 1.75 m person in front of a wall with a window. 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.

Camera Lens Focal length 40mm, fixed

Distance (m)

Scene

40mm on the OM System PEN frames 65 cm × 49 cm at 1.5 m: like 80mm on full frame, 24° across.

The subject is 1.5 m away; things behind it are drawn smaller, as the camera sees them.

Inside the frame: the picture you would get.

The numbers

Frame at 1.5 m65 cm × 49 cm
Full-frame equivalent80mm
Angle of view24° × 18°, 30° diagonal
Depth of field at f/2.81.45 m to 1.56 m (11 cm)
Depth of field at f/81.36 m to 1.68 m (32 cm)
Hyperfocal at f/2.839.6 m
Hyperfocal at f/813.9 m
Circle of confusion0.014 mm

Depth of field: what is acceptably sharp, wide open and at f/8, focused on the subject.

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.