Hyperfocal Distance and Depth of Field Quiz

The hyperfocal distance is the focus distance that puts the far edge of acceptable sharpness exactly at infinity. Focusing there gives the deepest possible depth of field for a given aperture and focal length. It is not the lens's minimum focus distance.

When you focus at the hyperfocal distance, everything from about half that distance to infinity is acceptably sharp. For example, focusing at 4 meters makes things sharp from about 2 meters to the horizon. Sharpness does not reach all the way back to the lens.

At very small apertures, light bends as it passes through the narrow opening, a phenomenon called diffraction. The result is softness that becomes visible at about f/16 and worsens progressively at f/22 and smaller.

With the same lens and f-number, depth of field shrinks quickly as the subject gets closer, which is why close-up and macro work has so little in focus. Stepping back does the opposite.

At the same subject distance and f-number, a longer lens magnifies the subject more, and greater magnification means shallower depth of field. That is why a telephoto lens blurs the background more readily than a wide angle lens from the same spot.

Depth of field changes most dramatically with subject distance. Halving the subject distance roughly quarters the depth of field, which is why close-up work has such shallow focus even at moderate apertures.

Focus stacking combines several frames focused at different distances, keeping the sharp part of each. The result has more depth of field than any single exposure could give, which is especially useful in macro and landscape work where stopping down further would cause diffraction.

The circle of confusion is the largest blur spot that still looks like a sharp point at a given print size and viewing distance. Depth of field calculations use it as the threshold for acceptable sharpness, so a stricter value gives a shallower calculated depth of field.

Each full stop halves the light. f/2 to f/2.8 is one stop and f/2.8 to f/4 is another, so f/2 to f/4 cuts the light by two stops, to a quarter. It also gives noticeably more depth of field.

Most lenses are sharpest a couple of stops down from wide open, around f/5.6 to f/11, so landscape shooters work there and focus carefully, often near the hyperfocal distance. If that still is not enough depth, they stack several frames. Always using f/22 trades away detail to diffraction.

A lens's sweet spot is the aperture range where it resolves the most detail, usually two to three stops down from wide open. Wide open, aberrations soften the image; at the smallest apertures, diffraction does.

Diffraction softness comes from light spreading as it passes through a very small aperture, so opening up to a smaller f-number is the direct fix. Moving from f/22 to around f/8 or f/11 usually restores crisp detail. ISO, shutter speed and white balance do not affect diffraction.

Depth of field extends only so far behind the point of focus. Focus too close in a landscape and the far edge of that zone falls short of the horizon, so distant mountains or sky detail turn soft. Focusing nearer the hyperfocal distance avoids this.

Depth of field gets shallower with a wider aperture, a closer subject and a longer focal length, and those three together give the strongest background blur. ISO and shutter speed change exposure, not depth of field.

Hyperfocal focusing is used when you want as much of the scene as possible sharp, from a close foreground out to infinity, as in landscapes and street scenes. It is the opposite of what you want for creamy background blur.