Photography Calculator

Depth of field is the zone in front of and behind your focus point that still looks acceptably sharp. It isn't a hard edge — sharpness falls off gradually — so "acceptable" is defined by a circle of confusion, the largest blur spot that still reads as a point at normal viewing. This calculator uses the full-frame standard of 0.030mm. From that, the focal length, the f-number, and your subject distance fix the near and far limits of the in-focus zone.

Three things drive depth of field, and they don't contribute equally. Aperture is the obvious lever: stop down from f/2.8 to f/8 and the zone deepens because the narrower the cone of light, the smaller the blur from out-of-focus points. Subject distance matters even more — depth of field grows roughly with the square of how far away you focus, which is why a landscape at 30 metres is sharp front-to-back while a flower at 30 centimetres has paper-thin focus at the same aperture. Focal length tightens it too: longer lenses render shallower depth at a given distance and framing.

The zone is not centred on your subject. The far limit always sits farther behind the focus point than the near limit sits in front — classically about a third in front, two thirds behind, though the exact split shifts with distance. As you focus farther out, the far limit races toward infinity faster than the near limit moves, until at the hyperfocal distance the far limit reaches infinity and everything beyond H/2 is sharp. Focus past that point and this calculator reports the far limit as ∞.

A practical note on the circle of confusion: 0.030mm is right for full-frame. A crop sensor enlarges more to reach the same print size, so it needs a stricter (smaller) circle, which slightly shrinks the calculated depth of field at the same settings. For everyday full-frame and mirrorless work the 0.030mm value is the standard, and it's what the numbers below assume.