What is Depth of Field? Complete Guide for Photographers

Depth of field is the range of distances in a photo that look acceptably sharp. Strictly speaking only one distance is ever in perfect focus. Sharpness falls away gradually on either side, and depth of field is the stretch where you stop noticing the blur. That is why the definition comes with a footnote: "acceptable" depends on how large you print and how closely you look, which the circle of confusion post explains.

A shallow depth of field isolates a subject, which suits portraits. A deep one keeps a scene sharp from front to back, which suits landscapes. Three things control it, and it helps to see them with numbers. All the figures below are for full frame.

Aperture

A wider aperture, meaning a smaller f-number, gives a shallower zone. With a 50 mm lens and the subject 3 m away, the zone in focus is about 37 cm at f/1.8, 58 cm at f/2.8, 1.2 m at f/5.6, 2.6 m at f/11 and 4.7 m at f/16. If the f-numbers feel backwards, think of them as fractions: f/2 is a bigger opening than f/16, the way 1/2 is bigger than 1/16.

Distance to the subject

Closer means shallower, and faster than most people expect. With the same 50 mm at f/2.8, the zone is about 6 cm at 1 m, 25 cm at 2 m, 58 cm at 3 m, 1.6 m at 5 m and over 7 m at 10 m. While you are close, doubling the distance roughly quadruples the depth. It is why macro work has a zone measured in millimetres.

Focal length

At the same distance and aperture, a longer lens gives a shallower zone. At f/2.8 with the subject 3 m away, a 24 mm lens gives about 3 m, a 50 mm about 58 cm, an 85 mm about 20 cm and a 135 mm about 8 cm.

But a longer lens doesn't always mean less depth

That last comparison hides a catch. In practice you frame the subject the same way whatever the lens, which means standing further back with a longer one, and the two effects cancel almost exactly. Frame a head-and-shoulders portrait at f/2.8 on full frame and the zone in focus is about 6 cm whether you use 35 mm, 85 mm or 135 mm. What the longer lens changes is how blurred the background looks, which is a separate matter covered in the bokeh guide. For the same framing, aperture and sensor size set the depth of field, and focal length does not.

Sensor size

Sensor size follows the same logic. Put a 50 mm lens at f/2.8 on an APS-C body and the zone shrinks from 58 cm to 37 cm, because the smaller sensor uses a stricter definition of sharp. But to frame the same shot on APS-C you would use a 33 mm lens, and that gives about 86 cm. So at the same framing and f-number, a smaller sensor gives more depth of field, which is why full frame looks shallower. The full frame versus crop sensor post goes through it.

Where it matters

In portraits, an 85 mm lens at f/1.8 from 2 m has a zone about 5 cm deep, which is less than the distance from nose to ears. Faces usually work better at f/2 to f/2.8, as the portrait aperture guide explains.

In landscapes you want everything sharp, so you use a smaller aperture and focus at the hyperfocal distance. A 24 mm lens at f/11 focused at about 1.8 m is sharp from about 0.9 m to infinity. The hyperfocal distance post shows how to focus in practice, and best aperture for landscapes covers when to stop down and when not to.

In macro work, the whole zone at 1:1 and f/8 is under a millimetre deep. That is where focus stacking comes in.

What "acceptably sharp" means

Out-of-focus points of light show up as small discs. The circle of confusion is the largest disc that still looks like a point at a normal viewing size. Full frame conventionally uses about 0.03 mm, and smaller sensors use proportionally less, which is why the calculator asks which camera you have. Print large or inspect at 100 percent and the actual limit is tighter than any table says, so treat the near and far figures as a guide rather than a guarantee.

Common questions

What is depth of field in photography?

Depth of field is the range of distances in a photo that look acceptably sharp. Only one distance is in perfect focus, and sharpness falls away gradually on either side, so depth of field is the stretch where the blur is too small to notice.

What controls depth of field?

Aperture, distance to the subject, and focal length control it. A wider aperture, a closer subject and a longer lens each make it shallower. For the same framing and the same sensor, aperture sets the depth of field and focal length makes no real difference.

What aperture gives the shallowest depth of field?

The widest aperture your lens allows, the lowest f-number such as f/1.4 or f/1.8. At f/1.8 with a 50 mm lens and a subject 3 m away on full frame, only about 37 cm is acceptably sharp.

Does sensor size affect depth of field?

Yes. At the same framing and the same f-number, a larger sensor gives a shallower depth of field. A full-frame camera at f/2.8 is shallower than an APS-C camera at f/2.8 framing the same shot, because the APS-C camera uses a shorter lens.

Related reading: Hyperfocal Distance Explained, Aperture vs Distance: What Affects DOF More?.