A guide to back button focus

If there’s one thing you want to perfect in your photos, it’s focus. It doesn’t matter whether the lighting is spot-on, your composition is great or your subject’s expression is unforgettable. Focus that’s even slightly off can spoil an otherwise brilliant image.

Even in this age of sophisticated autofocus systems, however, achieving sharp focus can be a challenge for many.

The good news is, there’s a simple trick that can help make the job of focusing much less error-prone and much more efficient. It’s called back button focus, and it could forever transform the way you shoot.

Back button focus

What is back button focus?

By default, virtually all cameras (when in autofocus/AF mode) will focus when you half press the shutter button, then take the photo when you fully press the shutter button.

A lot of people don’t realise that, in most advanced amateur to professional cameras, you can usually change this default setting. Instead of using a single button to activate focus and fire the shutter, many experienced shooters opt to remove the focus function from the shutter button and assign it to a different button on the back of the camera (e.g. AF-ON, AE AF, AF-L or AE-L).

The result? One button locks focus while another takes the photo. This is known as back button focus, and it comes with some major advantages.

Why use back button focus?

So why would you want to use two buttons to do the default job of one?

Essentially it comes down to better efficiency and control.

Your focus will stay locked

Your focus will stay locked

With the default setting (one button in charge of both the focus and shutter functions), things have to follow a set order:

  1. Set focus
  2. Half-press shutter button to lock focus
  3. Full press shutter button to take photo

This also requires you to keep the shutter button half-pressed to maintain focus.

If you happen lose focus (e.g. you accidentally release or trigger the shutter button, or something comes between your camera and subject, confusing your camera’s AF system) you need to set and lock focus all over again. In the time this takes, you could well miss the shot.

With back button focus (i.e. separate focus and shutter buttons), it’s possible to set focus, keep it locked and take the shot simultaneously, without looking away from the viewfinder. Simply activate focus with your thumb and the shutter with your index finger.

You don't need to constantly refocus

You don’t need to constantly refocus

Say you’re photographing a stationary subject (e.g. a portrait sitter, a landscape, or a plate of food) and want to create a few different compositions. Each time you adjust your framing you’ll need to also adjust your focus – either by moving your focus point, using the focus and recompose method (i.e. half pressing the shutter button to lock focus before reframing the shot), or pressing down the AF-L (autofocus lock) or AE-L (auto exposure lock) button.

While these methods work, they can be tedious and time-consuming.

With stationary subjects, back button focus locks focus with a single press of the focus button. As long as your subject remains within the plane of focus (i.e. the distance between it and your camera stays the same), your subject will stay sharp and you can freely change your composition without needing to press other buttons. (Care should be taken when using shallow depth of field, however.)

You can switch easily between single and continuous focus

You can switch easily between single and continuous focus

Cameras have at least two autofocusing modes: single AF for still subjects, and continuous AF for moving ones. Trouble is, changing focus modes takes time that photographers usually can’t afford. On top of that, each mode has limitations; single AF mode struggles when movement occurs, while continuous AF mode often trips up when your subject and active AF points don’t align.

Back button focus essentially gives you the best of both single and continuous AF modes, at virtually the same time. All you need to do is have your camera constantly set in continuous AF mode. Simply press and release the back focus button to focus on a still subject (and recompose as desired) or press and hold to track movement, releasing only if your subject stops moving.

Again, provided your subject stays within the plane of focus, it will come out sharp.

How do I set up on my camera?

How do I set up back button focus on my camera?

The process of setting up back button focus will vary from camera to camera, even those from the same manufacturer. To help guide you, here are some basic instructions that should be similar for modern camera models of each major brand.

(For full details please consult your camera’s manual.)

Canon Cameras

  1. In the Menu, navigate to Custom Functions (C.Fn)
  2. Go to Custom Controls
  3. In the Custom Controls menu, set the shutter button to “metering start”. This will stop the shutter button from triggering focus.
  4. Set the AF-ON button to “metering and AF start”.

Fujifilm Cameras

If your Fuji camera has a dedicated AF-ON button:

  1. In the Menu, go to Set Up (wrench icon)
  2. Select Function (Fn) Setting and check that “AF-ON” is set to “AF-ON”
  3. Select Button/Dial Setting
  4. Set Shutter AF to “Off” for both AF-S and AF-C

If your Fuji camera doesn’t have a dedicated AF-ON button:

  1. In the Menu, go to Set Up (wrench icon)
  2. In Button/Dial Setting set Shutter AF to “Off”
  3. Return to Set Up
  4. In Button/Dial Setting, select Fn/AE-L/AF-LButton Setting, and assign AE-L or AF-L button to “AF-ON”.

With Fuji cameras it’s possible to operate back button focus while in manual focus mode. Here’s how to set it up on your camera:

  1. Set the focus selection dial to Manual (M).
  2. Open AF/MF in the menu
  3. Select Instant AF Setting
  4. Set “AF-C”

Nikon Cameras

If your Nikon camera has a dedicated AF-ON button:

  1. In the Menu, open the Custom Settings Menu (pencil icon)
  2. Select the Autofocus tab
  3. Select AF activation
  4. Select AF-ON only
  5. Click right and set Out-of-focus release to “Enable”.

If your Nikon camera doesn’t have a dedicated AF-ON button:

For Nikon models that don’t have an AF-ON button, you will need to set up the AE-L / AF-L button in the Custom Settings Menu to use it as if it was an AF-ON button:

  1. In the Menu, open the Custom Settings Menu (pencil icon)
  2. Select the Controls tab
  3. Select Assign AE-L/AF-L button
  4. Scroll down to AF-ON
  5. Click on AF-ON and select “OK”.

Olympus Cameras

  1. Press Menu button
  2. Scroll down to Custom Menu (cog icon)
  3. Scroll across to A1, then across and down to AEL/AFL
  4. Scroll across again and select S-AF (single autofocus)
  5. Scroll across again and set the mode to “Mode 3”. This removes focus activation from the shutter button.
  6. Press OK button once complete.

Panasonic Cameras

  1. In the Menu, navigate to Custom settings (wrench icon beside the letter C)
  2. Scroll down to AF/AE Lock and set it to “AF Lock”
  3. Scroll down to AF/AE Lock Hold and set it to “On”
  4. Scroll down to Shutter AF and set it to “Off”

Sony Cameras

  1. Click on the Menu button
  2. In the first Menu tab scroll over to AF2 screen
  3. Scroll down to AF w/shutter and set that to “Off”
  4. Open Custom Key Settings menu item
  5. If your camera has a dedicated AF-ON button (Sony a9, a7 III onwards), select AF-ON from the list.
    If your camera doesn’t have a dedicated AF-ON button (Sony a6000 series and below), select AEL Button.
    If your camera has neither an AF-On nor AEL button (a7 II), select the C3 button.
  6. In the following menu, change the button setting to “AF-ON”.

Back button focus

How to focus using back button focus

Once back button focus is configured on your camera, set your camera to continuous focus mode. Then:

To focus and recompose

  • Press back focus button to acquire focus, then release
  • Recompose shot as desired
  • Press shutter button to take photo

For moving subjects

  • Press and hold the back button to track your subject
  • Keep back focus button pressed while you press the shutter button

In Conclusion

Back button focus is a fantastic method for dealing with complex or fast-evolving scenes, particularly weddings, events, sports/action, or wildlife photography. While not necessarily for everyone or every situation, it’s one of the handiest tricks you can ever learn as a photographer.

Once you get used to it, back button focus can really speed up your workflow and reduce focusing errors. There’s much less fiddling with focus points or settings, even if other elements get between you and your subject. The milliseconds this saves can be the difference between capturing and missing that perfect shot.

Give it a go and see what difference it makes to your focusing technique.

Want more advice on back button focus or help with setting it up on your camera? Get in touch or come visit us in store

Images by Louise Wright, Jonathan Borba and Team CameraPro