Back button focus is often used by advanced photographers as it provides a means to have separate control of the autofocus and shutter release.
By default Canon EOS cameras use “front button focus”; the shutter release button activates the autofocus and exposure metering. The shutter button has two distinct switch levels, so-called “half press” and full press.
When using the camera for static subjects photographers need to select ONE-SHOT focus mode, and for moving subjects that need to be tracked then AI SERVO is used. Switching between ONE-SHOT and AI SERVO as action happens in front of your camera will slow you down. Back button focus eliminates the need for switching focus modes.
Where is the back button?
EOS 1200D back button focus – circled in red
EOS-1D X back button focus – circled in red
The back button was historically the AE lock button, marked with a *. Since the EOD-1D Mark III some cameras have two buttons; AF-ON and the * button. Both buttons can be configured to provide back button focus depending on your thumb length.
For the EOS 7D, EOS 5D Mark III and EOS 70D I often configure both back buttons to work the same – it helps me when I’m switching between cameras with slightly different button placements.
ONE SHOT & AI SERVO autofocus
First it is necessary to understand the two main kinds of autofocus, one for tracking moving subjects and one for static subjects. If you already know about this then skip ahead.
read more about ONE SHOT & AI SERVO autofocus modes
ONE SHOT – Half press the shutter to activate the AF using ONE SHOT focus and the camera will acquire focus and then lock the AF on that subject while the shutter button is kept “half pressed”.
This allows a photographer to recompose their image but keep the focus locked on the subject, even if the AF point moves off the subject. This process is sometimes referred to as focus lock & recompose.
AI SERVO – Half press the shutter to activate the AF using AI SERVO focus and the camera will acquire focus and keep tracking the subject while the shutter button is kept “half pressed”.
If you try to change the composition of the picture and move the AF point off the main subject the camera will reacquire AF on the new subject under the AF point.
AI SERVO focus also determines if the subject is moving, the speed of movement and the direction to or away from the camera. With this is can predict where the focus needs to be when the actual picture is made.
There is a third AF mode; AI FOCUS. In my experience it tends to work like ONE SHOT focus most of the time and rarely and unpredictably decides to switch to AI SERVO mode. I prefer to be in charge of the focus on my camera.
Back button focus setup
The ability to change which button controls the AF is a Custom Function (C.Fn) and more recent cameras have also offered an additional way to configure it via the Custom Controls settings. These customisations are only available when a camera is used in the P, Tv, Av, M, B or Custom Shooting Modes.
Custom function to set back button focus on the EOS 650D
Custom controls to set back button focus on the EOS 70D
Custom Function back button focus
In the case of the single custom function there are four options available. It’s simple to read this as the text before the / is the function on the shutter button at half press, and the text after is the function on the * button. So options 1 and 3 will move the AF to the back button, and have either AE lock or not on the shutter button.
If the subject is in a consistent light and you shoot in Av, Tv, or P modes then you can select option 1 and for a sequence of pictures each frame will have the same exposure. In a floodlit stadium the light is pretty consistent so this is a reasonable approach.
If you choose option 3 there is no AE lock, so as a subject moves from light to dark while you track it the metering will adapt for each frame. If your subject is a performer on stage and the lighting is changing then this is a better approach to back button exposure.
Custom controls back button focus
The options available for cameras with multiple back buttons and custom controls are extensive. Typically the shutter button can be assigned to AF and AE lock, exposure metering start or exposure metering lock.
The back button(s) have more functions depending on the camera model.
Using back button focus
Back button focus makes AI Servo AF usable for both moving and stationary subjects
[tweet this]
Back button focus is most commonly combined with AI Servo AF. When the back button is pressed the AF is tracking the subject, but when you want to pause or recompose the scene you simply lift your finger off the back button and recompose the frame prior to taking the shot. Back button AF makes AI Servo AF usable for both moving subjects and stationary ones.
If you shoot and your subject passes behind a closer object as you track then release your thumb off the back button and press it again when the subject is visible again. This tops the AF system going off the intended subject but also requires some practice.
In my experience switching from front button to back button focus takes time to be instinctive
If you lose patience due to missed focus you won’t develop the muscle memory to use it correctly. If you have a battery grip on your camera take care as the buttons are sometimes slightly different in feel or placement.
Also if another person is asked to take a photo with your camera they may take out of focus pictures if they expect focus on the shutter button. Switching back to automatic “green square” or creative auto modes will deactivate back button focus until P, Tv, Av or M is selected again.
I often find the need to think about whether I need AE lock or not on the shutter button. But perhaps I just need to use manual exposure mode even more often.
Further reading…
- Canon USA’s Digital Learning Centre also explains back button focus
- Back button focus for action and sports photography
[…] button. My buddy and Canon expert, Brian Worley, has written an article on just how to set up back button focus with Canon, on his blog. On many DSLR’s it’s an option to program a button to do this in your […]
Thanks a ton!
Just a comment… not enough out there for those of us with old models… so its page 158 in Canon EOS 1000D manual/ EOS Rebel XS!]
Cheers
Well I read it!!! got the iso and fstop sorted. Now for mf. This week ‘s project is to re read and master this!!! Got the calibration done! Delighted!
[…] muligheten til det. Det tok litt tid før jeg ble vant med det, men nå klarer jeg meg ikke uten. How to setup and use back button focus HiFi: Hegel H80 og Dali Rubicon 2 med Mac Mini som kilde. Hodetelefonrigg: Sonos Connect, […]
Hi Brian – Please be so kind and explain to me how to set up Back button focusing on my Canon EOS 1200D.
Thank you in advance.
Best Regards
Kobus
Hi Kobus,
I just put the steps you need to setup back button focus for your EOS 1200D here http://www.p4pictures.com/2016/01/how-to-configure-back-button-focus-eos-1200d/
Brian / p4pictures
Brian can you tell me how to change it back from the back button focus to its original way on my canon t3i camera.
Hi Valerie,
To switch off back button focus on the T3i / 600D then you need to go in to the camera menu, find the custom functions, and set C.Fn 9 Shutter/AE lock button to 0.
Brian / p4pictures
Hi Brian. Do on you know if I’m able to setup back button focus on a Canon sx40 powershot, and if so where I can obtain the procedure steps? Thanks, Matthew (:
Hi Matthew,
Sorry I’ve had a good hunt through the PowerShot SX40 instructions and have not found a way to enable back button AF on the camera. The only thing I did find is that it is possible to assign AF lock to the ‘S’ shortcut button.
Brian / p4pictures
THANKS SO MUCH. I’ve read articles about this for two days but nothing could find a solution to my problem. They missed a few steps or something. Now, I have my answer. 🙂
Hi Brian,I own a 5DM3 should I have to reset it back on BB focusing after each shot, I set it with the second one down AF_ON. After I have shot with that to then goes back to the one above it, the little birds eye. I’ve also noticed in the screen before that the Custom Controls has a dash next to it and not a tick, like the Multi function lock..Can you please ne mark
Hi Jan,
You need to do two things to setup back button focus.
1. Switch off the AF from the shutter button – top one looks like the “birds eye”. Set this to either metering start or AE lock
2. The AF-ON button should be set up for back button AF by default, if not then make sure it’s set for Metering and AF start.
That should fix it.
Brian / p4pictures
Hi,
Just checking if you can use BBF with One Shot autofocus. I ask this because on a Canon 80D in AI Servo both the focus beep and the light in the viewfinder are disabled. Even the red light of the focus point is less obvious in AI Servo.
Regards Tony
Hi Tony,
Absolutely yes, you can use back button focus with one-shot AF.
Given that I turn off the beeps the camera makes first time I put a battery in a camera then I don’t notice the lack of beeps.
Brian / p4pictures
So what happens if you hold down the back button in One Shot Mode?
(In AI Servo I know holding down the Back Button gives continuous focusing till you let go)
Thanks for your help
Hi Tony,
If you hold the back button down in ONE-SHOT focus, then once the focus has locked it will stay locked. This is just like it would while you kept your finger on the half-press position of the shutter if you were using “front button focus”.
Brian / p4pictures
I have a Canon70D, I am a beginner, can you please help me how to set up the back button focus. I keep messing up on the focus.
Hi Gracie,
Your EOS 70D has Custom Controls, so navigate to Custom Functions in the menu, the orange tabs. Select C.Fn III: Operation/Others and choose number 4, Custom controls.
You need to select the shutter button – the first icon shown on the top left column – and set this to Metering Start.
Your AF-ON button should show the metering symbol and AF by default so that’s all you need. Pressing the shutter has no effect on focus.
Hope that helps.
Brian/p4pictures
Everyone retelling this BBF story seems to make the same statement that the AF On button will make going from single shot to ai-servo faster. If you are in Ai-servo mode to begin with then the shutter button by default will track the subject, no change there.
The idea of BBF is that you don’t need to refocus when you want to have your subject off centre. Of course, this was usually done by focusing, keeping the shutter half pressed and recomposing, then fully depressing the shutter button, so it’s the same thing. BBF means you can just press AF-On to focus and let go, recompose and press the shutter when you’re ready. Of course the shutter button now will not try to refocus, that’s what it’s about, not going from one shot to ai-servo.
Hi Alan,
Thanks for the comment. I think most people, me included, write about back button AF that way.
However on some of the newer cameras actually it is possible to switch focus from ONE-SHOT to AI SERVO. You need to have the right camera, and dig deep in the custom controls but with the 7D2, 5D4, 5DS/R and 1DX2 is it possible. See here: http://www.p4pictures.com/2014/11/back-button-af-eos-7d-mark-ii/
With these cameras and this setup if you press the back button and hold it then the camera will track. However for general photography with the camera set to ONE-SHOT the shutter button works and does focus lock and hold as many are used to.
Thanks for taking the time to comment.
Brian/p4pictures
If you are taking a single shot then using front-button or back-button focus, you focus, recompose, then take the picture. So long as you are in single-shot mode.
If you are taking a series of photos, waiting for the right moment between them, then with front-button focus you focus, recompose, take the first picture; then focus again, recompose again, then take the second picture; etc. This is because you can not keep the shutter button “half pressed” between the first picture and the second. With back-button focus, you focus, recompose, take the first shot, then wait and take the second shot, then wait and take the third, etc.
Where back-button focus helps is that all of the above works identically if you are in AI-Servo mode. So if after the third shot you want to switch to tracking focus on a moving subject, you just aim at that moving subject and hold the back focus button down while clicking the shutter away; in front-focus you need to switch the focusing mode then hold the shutter halfway down until the right moment, etc.
So I think that both ways of explaining BBF are correct. It allows you to quickly change between a “one shot focus” kind of shot and an “AI Servo” kind of operation. It also allows far more efficient focus-and-recompose.
Wow! I learned more from this article than I have in a very long time. Clear, great explanations! Thanks!
[email protected]
I have set up back button focus but the focus point jumps to the middle every time. Why is this?
Hi Estelle,
There’s two possibilities that I can see…
1. You’ve set the multi-controller to jump to the centre AF point when it’s pressed in, and are pressing this not the AF-ON or * buttons
2. When you set the AF-ON or * button on some cameras you can see INFO in the display and then you can set what AF point is selected when the button is pressed. It’s labelled as the AF start position on the 5D4 and 7D2. There are two options, manually selected AF point and registered AF point. If you choose registered AF point and don’t register an AF point then the camera assumes the centre point is the registered one.
I think you’re more likely to have the second of these two.
Brian/p4pictures
Thanks for this article. Can I please check that with a 7D where It’s not possible to assign servo or one shot to a specific back button, you recommend setting the camera’s main menu setting to servo, use af-on to track and shutter simultaneously if subject moving, or release af-on and press shutter if subject stops… and even though the camera is set to servo, it will auto switch to one shot?
I can’t work out the logic of that, but that seems to be the inference to explain how it is said that using bbf make switching from one shot to servo so easy… and why the ‘tweet this’ says bbf makes servo usable for moving and stationary subjects.
Thank you.
Most of the time I want focus and exposure to be acquired simultaneously (The main subject in focus and properly exposed). This would be you stadium example.
Therefore I want the shutter button of my 5D mark iii to ONLY take the image (and not acquire exposure). Is this what *(AE lock) does for the shutter button? or how is it archived.
Thanks.
Hi José,
If you are using AI Servo focus, there is no automatic lock of the exposure either with the front button or the back button. You would need to use the AE-Lock button, I would suggest seeing it to AE-Lock with hold, so you free up your thumb to pressing the AF-ON button.
Brian/p4pictures
I’m wondering if there’s a way to set up a t7i 800d for bbf
Hi Tyler,
Yes there is… and since you asked nicely I’ve just written a blog post on exactly how to do it for the EOS 800D/T7i and the EOS 200D/SL2.
https://www.p4pictures.com/2018/03/eos-800d-back-button-focus/
Hope that helps,
Brian/p4pictures
Hi I am using BBF on a EOS 1300D but would like to know, is it better to use Opt 1 AE Lock/AF or Opt 3 AE/AF No AE Lock. for shooting fast jets
many thanks
Hi Colin,
Since the light on the jets is not really changing while you shoot a series of frames I would choose option 1, this will lock the exposure on the first frame.
I would use Option 3 for a subject – typically ground based – that moves from shade to light areas while you shoot the burst of frames.
Brian/p4pictures
Thank you very much for explaining how to set up BBF on the Canon 70D ,it is so useful ,I am going to enjoy using it.
Do you by any chance have instructions on how to set up BBF on a Canon 60D please?