Back-Button Focus: What It Is and Why You Should Use It


You may or may not have heard of Back-Button Focus (BBF). Today I’ll explain what it is, why you might benefit from using it, and some direction in setting it up on your camera.

Switching to Back-Button Focus has the potential to speed up your shooting, while helping you focus more accurately and efficiently. Once you start to use it I doubt you would ever go back, personally I don’t leave home without it and it’s good karma for me to pass the gift on.


What is Back-Button Focus?

BBF is basically an alternative to focusing by assigning the auto focus function to a specific button on the back of your camera, on Canon 5D Mkiii this is the ‘AF-ON‘ (Some prefer to use the '*'star button). Instead of sticking with the typical default method, which is to half-squeeze the shutter button before taking a shot, it allows you to use your thumb to push (or hold) a button at the back of the camera to focus and takes the auto focus function away from shutter button completely.

It solved a problem for me I didn't consciously realise I had and allowed me to focus and shoot much more effectively. Interestingly, I’ve noticed it’s very rare to meet a pro that isn’t using BBF.


The Benefits of Back Button Focus

1. The Ability to Focus Then Recompose

Here’s an example of the problem you would have with the traditional ‘half-squeezing the shutter button’ method of focusing – What if you wanted to focus on a subject that is outside your chosen focus point? - By recomposing then half-squeezing the shutter button again outside that focus point will force the camera to re-focus on whatever is then inside that focus point, causing your subject to be out of focus. 

This is by far the biggest selling point of BBF - being able to focus on a subject then recompose your image before taking the shot, then when you choose to take the shot your focus is unaffected by pressing the shutter button. BOOM!


2. Increased Speed and Control of Your Camera

 Using BBF offers you more control of your focus and what you choose to focus on - when I’m shooting on location I move my camera around a lot in order to try various compositions, and BBF allows me to very quickly focus, recompose and shoot, sometimes once every second or two if I need to capture a scene very quickly.

Also worth noting, I generally find the closest focus point available to my subject first, especially if I’m shooting close to my subject or at shallow depth-of-field as there is then less movement required when recomposing and ensures my images are a sharp as possible.


3. AI Servo focus for ‘semi-autopilot’ focusing

Canon systems have the ability to shoot AI Servo Focus, which I sometimes find helpful as it is designed for moving subjects. It allows me to hold the back button down with my thumb continuously and the camera will automatically find the focus inside my chosen focus point. Then by lifting my finger off the back button the focus is then locked to that point. 

I see lots of Pro’s using this method so it’s worth trying out for yourself.

I sometimes enjoy using this method for portrait shoots where there is lots of moving around as it saves me pushing the back button quite so much and feels much more fluid, but takes time to master. 

The only down side of this method is you lose the ‘beep’ and red-blink to confirm the focus has been attained, which is hard to live without and you need to trust the accuracy and timing of you lens finding the focus.


How To Set Up Back-Button Focus

Here are set up instructions for setting up BBF on Canon, Nikon, and Sony. Hopefully the following directions are useful for you (I’m a Canon user), but for your specific camera model & manufacturer I would suggest asking YouTube or Google and you’ll get a detailed answer in a jiffy.

Please note for Canon Cameras – Some people prefer to choose either the ‘AF-ON’ or the ‘*’ button for BBF. 
Personally I use ‘AF-ON’ and the consensus says that’s the most popular method, but I have included both methods below so you can try them out.

Canon 5D Mkiii – ‘AF-ON’ option (my personal preference)
1.    Menu
2.    Custom Controls or C.Fn
3.    Select, ‘Shutter butt. half-press’ – then choose ‘Metering Start’
4.    Select ‘AF-ON’ – then choose ‘Metering & AF Start’
5.    Enjoy your new life as independent human.


Canon 5D Mkiii – ‘*’ star option.
1.    Menu
2.    Custom Controls or C.Fn
3.    Select, ‘Shutter butt. half-press’ – then choose ‘Metering Start’
4.    Select ‘*’ Star – then choose ‘Metering & AF Start’
5.    Enjoy your new freedom, you’ve earned it.


1.    Custom Settings Menu
2.    Select ‘a – Autofocus’
3.    Select ‘a4 – AF Activation’
4.    Select ‘AF-ON only’
5.    Congratulation, you made it, enjoy your new life.


1.    Custom Settings
2.    Custom Key Settings
3.    AEL Button, select AF ON
4.    In Custom Key Settings submenu, select AF/MF Button,
5.    Choose AF/MF Cntrl. Toggle.
6.    In Custom Key Settings select AF/ Shutter and select off.
7.    You are a star; go out into the world and shine.


So now you know all about BBF!
Let me know in the comments how you get on, and if you enjoy using the benefits of Back-Button Focus.