cst1 likes camerasAsk a question

What it frames

The Leica M EV1 with the Leica Elmarit-M 90mm f/2.8, 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.

90mm on the Leica M EV1 frames 60 cm × 40 cm at 1.5 m: like 90mm on full frame, 23° across.

24mm eq.50mm eq.135mm eq.90mm · like 90mm on full frame60 cm × 40 cm at 1.5 m
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 m60 cm × 40 cm
  • Full-frame equivalent90mm
  • Angle of view23° × 15°, 27° diagonal
  • Depth of field at f/2.81.48 m to 1.52 m (4.2 cm)
  • Depth of field at f/81.44 m to 1.56 m (12 cm)
  • Hyperfocal at f/2.8100 m
  • Hyperfocal at f/835.2 m
  • Circle of confusion0.029 mm
f/2.81.48 m to 1.52 m (4.2 cm)f/81.44 m to 1.56 m (12 cm)camerasubject, 1.5 m3 m
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.