Depth of field
How much of this will actually be sharp?
Pick the body, the focal length, the aperture and how far away the subject is. The answer below is the standard depth-of-field arithmetic with the crop factor applied to both the focal length and the f-number — the half of equivalence sensor size explained says almost everyone leaves out.
The shot
In focus
60 cm deep
- In front of the subject
- 27 cm
- Behind it
- 33 cm
- Hyperfocal distance
- 29.8 m
- Frame width at that distance
- 2.16 m
Focus at 29.8 m and everything from 14.9 m to infinity is acceptably sharp — the landscape photographer's trick, and the reason that number is on the page.
On full frame, this is
50 mm at f/2.8
Same framing, same depth of field, same total light. The exposure does not convert: f/2.8 meters as f/2.8 on every format. Field of view here is 40° across and 47° corner to corner.
How the sum works
- Sharp is a judgement, not a fact. Depth of field is the band where the blur circle stays smaller than the eye will notice in a normal print. The standard figure for that circle is 0.03 mm on full frame, and it is the convention every lens barrel and published table has used for decades. This page divides it by the crop factor for smaller formats, which is exactly why they hold more depth of field.
- The formulae. Hyperfocal distance is H = f² ÷ (N·c) + f. The near limit is s(H − f) ÷ (H + s − 2f) and the far limit s(H − f) ÷ (H − s), which runs to infinity once the subject is at or past H. Thin-lens formulae: they drift at true macro distances, where a real lens's pupil magnification starts to matter.
- More sits behind the subject than in front. Always, and the ratio widens with distance. The old "a third in front, two thirds behind" is only true at one distance for one lens; the bar above shows where the subject actually falls.
- Equivalence converts two numbers, not one. Multiply the focal length and the f-number by the crop factor and you have the full-frame lens that takes the same picture. A 25 mm f/1.8 on Micro Four Thirds is a 50 mm f/3.6 — and still meters as f/1.8.
The two action cameras and the premium compacts are listed under their one-inch class, which flatters the action cameras: their sensors are smaller still, so their real depth of field is deeper than the figures here.