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What it frames

The Pentax K-3 Mark III Monochrome with the Pentax HD DA 560mm f/5.6 ED AW, 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 sensor (23.5 x 15.6 mm) has a crop factor of 1.5, so the dashed frames are marked with the focal length that gives the same view on it.

560mm on the Pentax K-3 Mark III Monochrome frames 63 cm × 42 cm at 15 m: like 840mm on full frame, 2.4° across.

24mm eq. (16mm)50mm eq. (33mm)135mm eq. (90mm)560mm · like 840mm on full frame63 cm × 42 cm at 15 m
The subject is 15 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 15 m63 cm × 42 cm
  • Full-frame equivalent840mm
  • Angle of view2.4° × 1.6°, 2.9° diagonal
  • Depth of field at f/5.614.9 m to 15.1 m (15 cm)
  • Depth of field at f/814.9 m to 15.1 m (21 cm)
  • Hyperfocal at f/5.62979 m
  • Hyperfocal at f/82085 m
  • Circle of confusion0.019 mm
f/5.614.9 m to 15.1 m (15 cm)f/814.9 m to 15.1 m (21 cm)camerasubject, 15 m30 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.