How to Use Back Button Focus

In this step by step guide, Canon Photographer Kass Brumley shares everything you need to know about back button focussing.

The Advantages of Back Button Focussing

By setting up your camera for back button focussing you are removing the autofocus function from the shutter release button and assigning it to the AF-ON button on the rear of your camera. The main advantage of this is that it allows you to acquire, lock and maintain focus for multiple shots with your thumb while leaving your index finger free to release the shutter. In other words, you only have to focus once to shoot multiple shots of the same scene.

This is an advanced technique that makes focussing easier and more precise than the traditional shutter button half-press focussing method that requires you to refocus for each and every shot.

Back button focussing also makes switching between continuous focus mode (AI Servo) and single shot focus mode (ONE SHOT) quicker and more intuitive. This functionality really comes into its own when you need the ability to switch quickly between focussing modes while shooting both moving and static subjects.

How to Set Up Your Canon Camera for Back Button Focussing

Almost all cameras with a rear ‘AF-ON’ button, including the current line-up of Canon EOS DSLR and EOS R mirrorless cameras, can be set up for back button focussing.

Step 1: Disable Autofocusing from the Shutter Button

Out of the box, most Canon cameras are set up with metering and autofocus assigned to the shutter button. The first step of getting set up for back button focussing is to disable this.

To do so, simply navigate to the ‘Custom Controls’ settings via the ‘Quick Menu’ on the back of your camera or through the main menu.

The first selection in the ‘Custom Controls’ menu is called ‘Shutter butt. half-press’. You can change this by tapping the icon on the back of the LCD screen or pressing the ‘SET’ button in the middle of the rear multi-function wheel.

Step 2: Select ‘Metering Start’

While you are still in the ‘Custom Control’ menu, you will be able to select the ‘Metering Start’ option. Make sure that you tap ‘SET’ on your screen to confirm your selection, or hit the ‘SET’ button on your camera’s multi-function wheel.

Step 3: Assign Your AF-ON Button

On most Canon cameras, the ‘AF-ON’ button, also referred to as ‘rear AF’, will be enabled for focussing by default. However, it’s a good idea to double check that it is set up for ‘Metering’ and ‘AF Start’. You can now use your right thumb to focus with your camera’s ‘AF-ON’ button.

Step 4: Select a Focussing Mode

Now that you have all the buttons customised, it’s time to select a focussing mode. There are two main focussing modes to choose from:

a) ONE SHOT is a locking focus mode that’s popular for shooting weddings, landscapes, portraits, and other styles of photography where you have a controlled environment.

When using your rear AF button in ONE SHOT mode, your camera will perform similarly to when you focus by half-pressing the main shutter button.

When pressing and holding down your ‘AF-ON’ button in ONE SHOT mode, you will hear a beep that signals your camera has focussed (note that this beep can be disabled). You are then free to take a photo using the shutter button. When you want to take another shot, simply push the AF button again to refocus.

b) AI SERVO is a continuous focussing mode that’s popular with sports photographers, wildlife photographers and action photographers. When using back button focus, however, you have the advantage of being able to use the AI SERVO almost 100% of the time, regardless of what you are shooting.

To make AI SERVO behave like ONE SHOT, simply ensure your centre-weighted focus point is directed straight at your subject. Then simply hold down the ‘AF-ON’ button until your camera focuses, and release it once you have acquired focus. This allows you to lock and maintain focus, leaving you free to change your composition and take as many photos as you like. All you have to do to refocus on a new subject is hold down the ‘AF-ON’ button until it refocusses.

Going from front button focussing to back button focussing can take a little bit of practice, so be sure to take your time when setting it up in camera and give yourself some time to play around with it before shooting any major events.

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