Autofocus modes explained: single, continuous and tracking

Autofocus modes tell the camera whether to lock focus once or keep adjusting it while your subject moves. Single autofocus, often labeled AF-S, focuses when you press the shutter button halfway and holds that distance until the shot is taken. Continuous autofocus, often labeled AF-C, keeps measuring and adjusting focus for as long as the button stays partly pressed. Tracking extends continuous focus by trying to follow one subject across the frame, using distance and, on many cameras, the subject's shape or color to stay on it. Manufacturers use different names, so check your menu for the equivalent labels.

Choosing a mode is mostly a question of whether the subject will stay put. A landscape, a product or a seated portrait gives the camera time to lock focus once. A dog running toward you, a cyclist crossing the frame or a child on a swing changes distance constantly, so focus locked half a second earlier may already be wrong when you press the shutter.

Single autofocus for still subjects

Single autofocus is the sensible default for landscapes, architecture, food and posed portraits. Press the shutter button halfway, wait for the focus indicator to confirm, which may appear as a green dot, a solid box or a short beep, and then press the rest of the way. If the indicator never confirms, the camera is searching for contrast. Move toward an edge with more detail, add light or change the angle rather than pressing halfway again and again, because repeated attempts waste time and can cause you to miss the moment.

Low light and flat surfaces are the usual causes of hunting. A plain white wall, an empty patch of blue sky or a dim room gives the system little contrast to lock onto. Many cameras can project a small assist light in dim conditions, which helps the system find focus. Switching to manual focus with a magnified view or focus peaking is a reliable fallback when the camera simply cannot find contrast.

Single focus has one common pitfall, which is focusing and then recomposing. When you press halfway, lock focus and move the camera to a new framing before taking the shot, the distance has been set for the original position. For a near subject, that small change can move the plane of sharp focus off the eyes. A better approach is to compose the frame first and then move the selectable focus point onto the nearer eye, so focus is set after the framing is final. Alternatively, switch to continuous or tracking autofocus, so focus follows the subject as you reframe. Focus-and-recompose is usually fine for distant subjects, where a small change in framing shifts the focus distance by a negligible amount.

Continuous autofocus for moving subjects

Continuous autofocus is the mode for anything that changes distance. Hold the shutter button halfway and the camera keeps updating focus as the subject approaches, recedes or wanders. Many cameras pair it with burst shooting, so you capture a sequence and choose the sharpest frame later. The camera focuses on whatever sits under the focus point, so place the point on the subject. If the point lands on background, or a wide area lets the camera choose for itself, a fence post or a branch closer to the lens may take the focus instead.

Continuous focus also draws more power than single focus, because the camera keeps adjusting focus for as long as the button is held. On long outings with a lot of action, carry a spare battery.

Tracking and focus areas

Tracking adds the ability to follow a subject across the frame. Many cameras offer face and eye detection that can latch onto people and animals, and some let you select a subject that the camera then follows. Tracking works best when the subject is reasonably large in the frame and separates clearly from the background. It can be lost when something passes in front of the subject, or when the subject leaves the frame and returns, so keep the subject on the focus point and avoid switching targets in the middle of a burst.

Focus area choices work with every mode. A single point gives the most control and suits precise placement, such as an eye in a portrait. A small zone or group area gives the camera some tolerance for movement, while a wide area leaves more of the decision to the camera, which can be unpredictable. Many photographers also use back-button focus. It moves autofocus to a button on the back of the camera instead of the shutter button, so the shutter fires without refocusing each time, and focus can be held on a subject while you take several frames in a row.

A practical test is to photograph a moving object at a distance you can control, such as a pet running across a lawn or a friend walking toward you, and then count how many frames stayed sharp. That exercise shows whether the camera keeps up with the speed of your subject, and whether your chosen focus area is too small to hold it or so large that the camera wanders onto the background.

After a burst, review the sharpest frames at full size before deleting anything. A frame can look acceptable on a small screen and still show soft eyes or a blurred edge. If the focus stays on the subject but the frames are still soft, look at the shutter speed next. A speed that is too slow for the subject's movement records that movement as blur, whatever the focus does. Raising the speed reduces the light reaching the sensor, so you may need a wider aperture or a higher ISO to keep the exposure right.