Back Button Focus: Setup and Why It Helps Explained

Back button focus is a camera setup where autofocus is started by a button on the rear of the camera, usually the AF-ON button, instead of by half pressing the shutter. The shutter button then only takes the picture, so you can focus once, keep the focus locked, and shoot as many frames as you like.

Why It Matters

With the default setup, half pressing the shutter focuses and fully pressing it fires. That works well until you want to focus on a subject and then recompose, or switch between a still subject and one that moves. In single autofocus the lens locks on a half press, but in continuous autofocus it keeps refocusing, and each mode needs a menu change.

Separating the two jobs gives you one control for focus and another for exposure. You can hold the rear button to track a moving subject, release it to lock focus on a still subject, and press the shutter at any moment without the camera hunting. Many sports, wildlife and event photographers use this setup all day.

Beginner Setting Up Back Button Focus

Every brand names the settings differently, but the idea is the same. You remove autofocus from the shutter button and assign it to a rear button under your thumb.

Back Button Focus Setup Steps

1. Find the AF-ON button on the rear of the body, near the thumb rest. Some cameras use the AE-L or AF-L button instead.
2. Open the custom function or menu that controls the shutter button and turn off autofocus for half press. On Canon this is often called Shutter Button Function, on Nikon AF Activation, and on Sony Focus Hold or AF with Shutter.
3. Make sure the rear button is set to start autofocus, not just exposure lock.
4. Set the focus mode to continuous autofocus, such as AF-C or AI Servo.
5. Point at a subject, press and hold the rear button, then press the shutter to shoot.

What Changes In Use

Why Beginners Like It

• You can use one focus mode for nearly everything, instead of switching between single and continuous.
• Focus does not change when you press the shutter again for another frame.
• You can focus once on a spot, such as a doorway, and wait for a subject to walk into it.
• The camera will not refuse to fire because it could not find focus.

Common Mistakes

• Forgetting to press the button and taking out of focus pictures, which is the main adjustment problem for the first few days.
• Setting the rear button to exposure lock only, so nothing focuses.
• Using single autofocus and then expecting tracking when holding the button.
• Handing the camera to someone else, who will not know the setup. Switch back first.

A Quick Exercise

Set up the camera, then photograph a friend walking toward you. Hold the rear button while they approach, press the shutter in bursts, and then release the button and recompose with a still subject. Notice how the focus stays where you left it.

Handy for this: Fast Prime Lens — creamy backgrounds, low light. (affiliate link)

Advanced Advanced Use, Modes And Ways To Refine

Continuous Mode With A Lock

The most flexible method combines AF-C with the rear button. While held, the camera tracks movement. When you release the button, focus stays exactly where it stopped, behaving like single autofocus. You get both behaviors without touching any switch, and that is the biggest reason people adopt this setup. See continuous autofocus for tracking settings and autofocus area modes for choosing the focus area.

Using It For Recomposing

When you focus on a subject and then shift the camera to improve the framing, back button focus makes the lock reliable. The method has limits at wide apertures and close distances, because moving the camera changes the distance to the subject slightly. A full explanation, including when to avoid it, is in focus and recompose. For portraits, an eye detect mode often removes the need to recompose at all, as covered in eye autofocus.

Tracking Sensitivity And Zones

Because you decide when to start tracking, tune how the camera follows a subject. Reduce tracking sensitivity if objects often cross in front of the subject, such as players passing by. Increase it when the subject changes speed suddenly. The details are in AF tracking sensitivity. Combine with zones or subject detection, described in subject detection autofocus, for birds and vehicles.

Mirrorless And DSLR Differences

Both camera types support rear button focus, but mirrorless bodies add choices. Many let you assign different buttons to different focus areas, such as one button for a wide area and another for a small point. Some can also switch between eye detect and tracking at the press of a custom button. DSLR bodies may offer fewer buttons, but a dedicated AF-ON button is common on mid-range and professional models. Read DSLR versus mirrorless for other differences.

Using It For Video

In video, the shutter button is not used for focus anyway, and the rear button may start a one-shot autofocus pull while you record. Assign it so you can trigger a quick refocus, then switch to manual for precise work. See video autofocus and focus peaking and magnification.

Custom Buttons And Muscle Memory

Use a custom button for related functions, such as switching the focus area, and keep the main controls under the thumb and index finger. Practice at home with the lens cap off, and practice releasing the rear button to lock. After about a week, most photographers find the setup feels natural. Read custom buttons on the camera for ideas.

When Not To Use It

Casual users who mostly photograph still subjects and rarely recompose may not need it. Also, if several people share one camera, the default setup is less confusing. You can always assign the setup to a custom shooting mode and switch back with one dial turn. See custom shooting modes.

Try It

1. Find the setting that controls autofocus on a half press and turn it off.
2. Assign autofocus to the rear button and set the camera to continuous autofocus.
3. Photograph a moving subject while holding the button, then release to lock on a still object.
4. Take 20 pictures and count how many are sharp compared to your old setup.

Common Questions

What is back button focus?

It is a setup that moves autofocus from the shutter button to a rear button, usually AF-ON. The shutter button then only takes the picture, so focus and exposure are controlled separately.

Is back button focus better than half pressing the shutter?

It is more flexible, especially for action and recomposing, but not necessary for everyone. Many photographers find it more reliable once they are used to it.

Does back button focus work with autofocus modes?

Yes. It works best with continuous autofocus, because releasing the button locks focus like single autofocus. You can also use it with single mode if you prefer.

Why is my camera not focusing after I changed the setting?

Check that the rear button is assigned to autofocus and that the shutter button focus is turned off. Also confirm that the lens is set to autofocus, not manual.

Related Lessons

• Continuous Autofocus for tracking moving subjects.
• Autofocus Area Modes to pick the right focus area.
• Focus And Recompose for the limits of locking and shifting.
• Eye Autofocus to keep portraits sharp.
• Custom Buttons On The Camera to speed up your controls.