AF Tracking: How Your Camera Follows a Moving Subject

AF tracking is the autofocus setting that moves the focus point across the frame to stay on a subject you chose. You put the point on a cyclist, a dog or a bird, start focusing, and the camera shifts the point from place to place as the subject moves, so you can keep your attention on timing and framing instead of steering a tiny box with your thumb.

It matters because a moving subject does two things at once: it changes distance from you, and it changes position in the frame. Continuous autofocus handles the first. Tracking handles the second. The camera only keeps a moving subject sharp when both are working, and most of the confusion about tracking comes from treating them as one setting.

Two jobs: how far away, and where in the frame

Every autofocus system answers two questions. The focus mode decides when the lens refocuses: once and then lock (single AF), or again and again for as long as you hold the button (continuous AF, also called AF-C, AI Servo or C-AF). The AF area mode decides where in the frame the camera measures: one point, a group of points, the whole frame, or a point that follows the subject. Tracking is one of the area modes. Menus call it Tracking, 3D tracking, Whole area tracking, Lock-on AF or Tracking: spot, depending on the camera.

Here is the misconception this clears up. Continuous AF on its own does not move the point. With a single point and AF-C, the camera refocuses on whatever sits under that point, many times a second. If the runner drifts left and the point stays where it was, the camera now refocuses on the grass behind them. Tracking has the opposite gap: it decides where to measure, not when to refocus. That is why many cameras offer tracking only with continuous AF, and why the two are worth setting together.

Want the distance half in detail, including how the camera predicts where an approaching subject will be when the shutter opens? Continuous autofocus (AF-C) covers prediction, the focus budget, release priority and the settings that tune it.

How the camera knows what to follow

When you start tracking, the camera takes a snapshot of what sits under the starting point. From then on, many times a second, it looks for the same thing in the new view and moves the point to wherever the best match is. What it compares depends on the camera, but the cues are the same four:

• Distance. The autofocus system already measures how far away things are. A subject 20 m away is unlikely to become a fence 3 m away from one moment to the next, so a sudden jump in distance is treated with suspicion.
• Color and brightness pattern. A red shirt against green grass is easy to follow. A grey heron against grey water is not.
• Shape, through subject detection. Cameras that recognize eyes, faces, bodies, animals, birds or vehicles can follow the thing itself, not just a patch of color, and keep hold of it as it turns.
• Motion. The camera expects the subject to be roughly where its last few positions say it should be next, and searches there first.

The more of these cues set the subject apart, the better tracking works. A lone bird against open sky differs in every one of them, which is why the eagle above is about as easy as tracking gets. A player in a crowd of identical jerseys, all at the same distance, differs in almost none.

Where the camera gets this information has changed. A camera with an optical viewfinder has a separate autofocus sensor that sees only small patches of the scene, so it borrowed color information from its metering sensor to follow a subject between points. A mirrorless camera reads focus and color from the image sensor itself, so it sees the whole frame in detail at once. That is what made reliable subject detection possible, and why tracking on mirrorless cameras is usually far stickier. The underlying measurement is explained in how autofocus works.

Detection finds the subject, tracking keeps hold of it

Subject detection and tracking are often switched on together, but they do different things. Detection answers “what is a subject in this frame?” Tracking answers “which subject did you mean, and where has it gone?” With both on, the camera can follow an eye while it is visible, fall back to the head when the subject turns away, and fall back again to the body or simply the tracked pattern when even the head is too small or hidden. Detection needs the subject to be a reasonable size in the frame. A bird that fills a tenth of the width is far easier to recognize than one that fills a hundredth.

Shooting people or animals and wondering whether eye detection is doing the tracking for you? Eye detection AF covers how it finds the eye, when it gives up and how to set it up.

Starting, holding and ending a track

Tracking is something you start, not something that is simply on. The sequence is much the same on every camera:

1. Put the starting point on the subject. Tracking follows whatever you start it on. Start it on the background and it will faithfully track the background.
2. Start focusing. Half-press the shutter button, or press the AF-ON button if you use back-button focus. On many cameras you can also start a track by touching the subject on the rear screen.
3. Hold while you follow. The point moves with the subject as long as you keep the button down. Keep the subject in the frame yourself by turning with it.
4. Let go to end the track. On many cameras the point then returns to where you started it, ready for the next subject. If the box ends up on the wrong thing, letting go and starting again is the quickest fix there is.

Two settings change how far the tracker may roam. Some cameras let tracking follow the subject anywhere in the frame once it has started, even if you began in a small zone. Menus call this something like whole area tracking. Turned off, the tracker stays inside the area you chose. Roaming freely suits a single subject against a plain background. Staying inside a zone suits a busy scene where you would rather the camera lose the subject than wander off to something else. The other setting is how readily the camera gives up on the subject when something passes in front of it, usually called tracking sensitivity, blocked shot response or lock-on. It belongs to continuous AF and is covered on that page; the short version is to leave it in the middle until you have a specific problem.

Tracking moves the point, not the frame: why you still pan

Tracking can only follow a subject that is still in the picture. A subject crossing in front of you leaves the frame much sooner than most people expect, especially with a long lens. The table shows how long a subject moving straight across takes to cross the full width of the frame if you hold the camera still.

A sprinting dog at 300mm crosses the whole frame in under a quarter of a second. No tracker can help with that; the dog is simply gone. So the working method for anything crossing your view is to pan: turn your body with the subject so it stays roughly in the same part of the frame, and let tracking take care of the smaller drift within the frame that your panning cannot keep perfectly steady. Tracking is for the subject that moves around inside your composition, not a replacement for following it with the camera.

Turning with the subject is a skill of its own, and done at slower shutter speeds it blurs the background on purpose. Panning photography covers the stance, the swing and the shutter speeds.

Where tracking loses the subject, and what to do

Tracking fails in a handful of predictable ways. Knowing them tells you when to trust it and when to take the point back.

• Look-alikes. Two players in the same kit at the same distance, or two gulls in a flock, give the tracker nothing to choose between them, as the diagram shows. Start again on the right one, or use a single point and follow the subject yourself.
• The subject blends into the background. Tracking by color and pattern needs a difference to follow. A deer in brown undergrowth or a white bird against white cloud is hard. Subject detection helps; when it cannot recognize the subject, a single point held on it is more dependable.
• The subject is too small. A subject that covers only a few points gives the tracker little to compare, and detection may not recognize it at all. Get closer, use a longer lens, or start the track only once the subject is a reasonable size.
• Something passes in front. A post, a referee or a branch crosses the subject, and the tracker either jumps to it or loses the subject. A slower tracking sensitivity helps it ignore brief obstructions.
• The subject changes how it looks. A bird that turns from side-on to head-on, a gymnast who flips, or a cyclist who rides into shadow presents a different pattern from the one the camera stored. Detection copes with this better than color tracking alone.
• Dim light. Every cue gets weaker as light falls. Tracking hesitates and drifts before plain single-point focus does.
• Starting on the wrong thing. The most common failure of all: the start point was on the background or a nearer object when you pressed the button. Watch where the box is before you press.

Losing focus because the lens hunts all the way to its closest distance when the subject slips out of view? A focus limiter stops a long lens searching ranges your subject will never be in.

Tracking, zone or single point: choosing for the subject

Tracking is not automatically the best area mode for a moving subject. It is the best when the subject stands out and moves around within your framing. When the scene is cluttered or full of look-alikes, a smaller area that you steer yourself is often more reliable. The table pairs common situations with a starting choice.

• A single bird against open sky: Area mode to start with: Tracking or wide area, with bird detection if you have it. Why: Nothing else in the frame to confuse it, and the bird moves around the frame as you pan.
• A bird among branches: Area mode to start with: Single point, held on the bird. Why: Branches at a nearer distance steal any larger area.
• One player in a team sport: Area mode to start with: Tracking started on that player, or a small zone. Why: Look-alikes cross constantly; be ready to restart the track.
• A runner or cyclist on a predictable line: Area mode to start with: Zone, or tracking. Why: The subject stays where you expect it; either works if you pan.
• Children or pets moving around a room or garden: Area mode to start with: Tracking with face, eye or animal detection. Why: Erratic movement within the frame is exactly what tracking does well.
• Cars or bikes on a track: Area mode to start with: Tracking with vehicle detection, or a zone. Why: Strong shapes are easy to recognize; similar liveries can fool color tracking.
• A subject that is barely moving: Area mode to start with: Single AF with a single point, or eye detection. Why: Nothing to track; tracking adds a chance of the point drifting.

The deeper guide to the other area modes, and to placing points by hand, is in how to choose focus points. For why the center point is the most sensitive and how many points a camera really needs, see autofocus points. Settings for whole situations are gathered in camera settings for sports and camera settings for wildlife.

Photographing birds in particular, where a frame can hold open sky one moment and a tangle of branches the next? How to photograph birds covers fieldcraft, light and the focus choices for perched and flying birds.

Tracking in video

In video the tracker works the same way, but every focus change is recorded, so how it moves matters as much as where it lands. Cameras usually offer separate video settings for how fast focus travels and how quickly it switches to a new subject. A slow, sticky setting gives smooth, deliberate changes; a fast one keeps up with action but can make focus visibly jump when something crosses the frame. Touching the subject on the screen to start a track is the easiest way to move focus from one person to another during a shot. Video for photographers covers the rest of the move from stills to video.

Common mistakes with AF tracking

• Thinking continuous AF follows the subject across the frame. It refocuses on whatever is under the active area. If the area does not move, the subject leaves it.
• Starting the track on the wrong thing. The tracker follows what it starts on, background included. Check the box before you press.
• Holding on to a track that has gone wrong. Once the box is on the wrong subject, it rarely finds its way back. Let go and start again; it costs a fraction of a second.
• Expecting tracking to replace panning. With a long lens a crossing subject leaves the frame in well under a second. Turn with it.
• Using tracking in clutter. Branches, fences and crowds give the tracker more chances to jump. A single point you steer yourself often keeps more frames sharp.
• Judging tracking by the box on the screen. The box can sit on the subject while focus is slightly behind it. Check the frames at full size, not the overlay.

Try this: tracking against a single point on the same subject

You need ten minutes and something that moves around unpredictably: a dog playing, children running, or traffic and cyclists on a street seen from the pavement. Set continuous AF and a burst rate of a few frames per second, and use a fast enough shutter speed to stop motion blur, 1/1000 is a safe start.

1. With a single point, follow the subject for three bursts of about two seconds each, keeping the point on it yourself.
2. Switch the area mode to tracking. Start each track on the subject and follow it for three more bursts the same length, turning with it but letting the box do the fine aiming.
3. If you can, wait for a moment when two similar subjects cross, two dogs or two cyclists, and shoot one more tracked burst through the crossing.

Judge the result at full size on a computer, not on the camera screen. For each burst, count the frames where the subject’s eye or face, or the front of the bike, is sharp. Then look at where the focus point was in the failures; many cameras can show it in playback. If tracking scored better, the subject stood out well enough for it. If the single point scored better, look at what the tracker jumped to: that is the kind of scene where you will steer by hand. The crossing burst shows you directly how your camera handles look-alikes.

Want to check how well the ideas have settled? The autofocus systems quiz asks about tracking, phase detection and focus technique, with an explanation for every answer.

AF tracking questions

Is AF tracking the same as AF-C?

No, though the names are often used for each other. AF-C, or continuous AF, is the focus mode that keeps refocusing as the subject’s distance changes. Tracking is an area mode that moves the focus point across the frame to stay on the subject. You usually want both together for a moving subject.

Should I leave tracking on all the time?

Many people leave it on for general action and switch to a single point when the scene gets cluttered. For still subjects it adds nothing, and in busy scenes it can wander. Knowing which button or menu entry switches area modes quickly matters more than the default you choose.

Why does tracking jump to the background?

Usually because the track was started on the background, the subject was too small or too similar to its surroundings to follow, or something crossed in front of it. Start the track with the point clearly on the subject and, if it still jumps, try a smaller zone or a single point.

What is whole area tracking?

It is a setting on some cameras that lets a track, once started, follow the subject anywhere in the frame rather than only inside the zone or point area you chose. Turn it on for a single subject against a plain background. Turn it off when you would rather the camera stay inside your chosen area than chase something elsewhere.

What does lock-on mean in the tracking settings?

It describes how long the camera stays with its subject when something else appears at a different distance, such as a branch or a referee crossing in front. A locked-on setting ignores brief obstructions; a responsive one switches to the new object quickly. Leave it in the middle and move it only when one of those problems shows up.

Does tracking work with manual focus?

No. Tracking moves an autofocus point and relies on the camera refocusing as it goes. With manual focus you control the distance yourself, and the camera has nothing to steer. For fast subjects where autofocus struggles, zone focusing is the manual alternative.