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

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

If you spend any time surfing photography forums and Facebook groups, you will undoubtedly see a constant flow of questions asking for the best way to nail focus. Maybe you are one of those people that find themselves struggling. The trick is that most cameras have a setting that will help you focus like a pro. That trick is called back-button focus, and once you use it, you’ll never want to go back.

The Basics

When you get a camera and turn it on for the first time, it’s automatically set up with some default settings. One of the main settings that have become standard across the board is how your camera focuses. That standard practice is to halfway press the shutter button, the camera focuses, then you press the shutter down the rest of the way to take your image. What back-button focus does is remove the focus actuation from the shutter button and instead assign this function to a button on the back of the camera. Now when you shoot, you’ll press your back-button to lock focus and then press the shutter to take an image. If you don't press the focus button, your camera acts as if you have the camera set to manual focus. At the beginning, this may seem like you're over complicating things. I get it, why make it so that you have to use two buttons to accomplish what was done with one? But there are some very real benefits that make this change more than worth your while. 

No More Having to Constantly Refocus  

The first advantage comes when dealing with those certain compositions where your subject sits in the part of the frame where there is no focus point. In the past, you would have to focus, recompose, shoot. The problem here is that after that first frame if you release the shutter button all the way you will have to focus again the next time you press the shutter. So now you have to focus, recompose, shoot, repeat over-and-over again each time you press the shutter button. Another problem with this is that you are constantly moving the camera to lock focus which distracts you from fine-tuning your composition. With back-button focus, all you have to do is focus one time, recompose, and shoot until you're done. Unless your subject moves forward or back, you don't have to press the focus button again. Now you can shoot and make small adjustments to your composition while you shoot as needed without having to worry about focusing each time.

No More Having to Choose Between Single and Continuous Focus

One of the biggest struggles with autofocus comes from the use of single and continuous autofocus. Before, you had to choose what setting to use. If you needed to focus and recompose, then you had to choose single. This way you could half-press the shutter to lock focus, recompose, then take your image. But then if something with movement started to happen you would miss the shot because you didn't have the right focus mode.

If you had continuous autofocus selected, you would be fine for anything with motion as well as anything that was still. The problem here is that your subject had to be located in part of the frame where there was a focus point. If you needed to move the frame so that the focus point was no longer on the subject, the continuous autofocus would make the camera automatically refocus on wherever the focus point was placed.   

When you have back-button focus set up you actually get the benefits of both modes without any of the drawbacks. The way this works is that you have the camera always set to continuous autofocus. This way when you are tracking the movement of a subject you just hold down the back-button as you simultaneously press the shutter to capture images. When you run into a situation where you need to focus and recompose, all you have to do is press the back-button to focus, release the back-button, then recompose and shoot. Because the camera only focuses when you press the back-button, you’ll never have to refocus until you or your subject moves.

The Setup

While this process may vary from camera to camera as well as manufacturer to manufacturer, below is a short list walking through how to set this feature up. If you any of the below doesn't work for you, I suggest referring to your camera's owner's manual or doing a quick YouTube search for your specific camera.  

Nikon

For this, I’m referencing the Nikon D750 but it should be similar for most Nikons.

Menu - Custom Settings Menu (pensile) - f (Controls) - Assign AE-L/AF-L button - Press = AF-On and Press + Command dial = OFF

From here you select the AF-C focus mode from the AF selection button.

Canon

Menu - Custom Controls (C.Fn).

In this menu, you’ll need to do two things. First, you’ll remove the AF-ON from the shutter button by selecting the shutter button and set it to AE-Lock (*). Next, you’ll select the AF ON button and set it to AF. After this, you set your camera's AF mode to AF-C.    

Sony

The first step here is to remove the AF function from the shutter button. To do this we go Menu - Custom Settings (gear icon) - AF w/Shutter = OFF

Next, we need to assign the AF function to the back button. For this we go Menu - Custom Settings (gear icon) - Custom key settings - AE-L Button = AF ON. Now when the AF/MF / AEL lever is in the down (AEL) position, the button acts as the back-button focus.  

We can stop here if we want, but because Sony offers some nice features such as focus peaking when in the manual focus mode, we can also set a very quick and easy way to access this feature by going Menu - Custom Settings (gear icon) - Custom key settings - AF/MF Button = AF/MF ctrl Toggle. Now to quickly toggle between AF and MF, you can switch the AF/MF / AEL lever up to AF/MF and press the button once to switch to manual focus and then press again to switch back to autofocus.  

Fuji

The first step is to set the focus selection dial to M (manual). This will make it so the camera won't focus when you press the shutter.

Next, we need to make sure what focus mode is used when manual focus is selected. To do this we go Menu - AF/MF - Instant AF Setting - AF-C

Lastly, we need to decide what button we want to use to trigger the focus. Some cameras have the ability to map a custom button as AF on. For my X-PRO2, I have to use the AF-L button. For me though, The AE-L button is a better choice. Thankfully, you can swap these two buttons around so that the AE-L button acts as the AF-L button and vice versa. To do this, we go  Menu - Set Up (wrench) - Button/Dial Setting - AE-L/AF-L Button Setting - AF-L/AE-L

While this is a bit different because you have to set the camera to manual focus in order to use back-button focus, I do like that I can easily switch the camera from manual focus to single or continuous and the focus will be back on the shutter button. This is great for when you hand your camera to someone else to take a picture since that's what most everyone will be used to using.

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43 Comments

Brian Pernicone's picture

No doubt back-button focus is one of the best "tricks" of the trade.

Tony Northrup's picture

Great article and love BBF! But I do want to warn people that it works best with cameras that have GREAT continuous focusing systems. So, it's fantastic with a D750, but with a D3400, you're often better served by selecting AF-S for still subjects. Using AF-C all the time will definitely result in some missed shots. The same applies for cameras like the a7, a7 II, a7R II, T6, XT-1, XT-10, etc. Just don't want people to try it out and get frustrated because they missed focus.

Oh, and I *love* having two BBF buttons. One button set to a single AF point, and the second set to all AF points. That way, I never have to switch between different focus point groupings. The 5D III/IV/S, D850, a9, a7R III all let you do this.

Jason Vinson's picture

Very good point Tony! Thanks for chiming in!

I've noticed on my 5DIII I do end up with a tad more missed shots during a portrait session if I leave the camera in AI-servo vs moving to single shot. Your comment has cleared up some confusion for me now. Thank you!

Where can we find a setup guide for the two BBF buttons? One set to single point the other to a focus point grouping.

Alessandro Molinari's picture

I think I started to use BBF thx to one of your video. Did you ever use the BBF on a Sony as the a7R II with a Canon lens mounted? I doubt it works perfectly...

With Sony there is an alternative way to do this, without any custom settings or button changes to create a back-button.

Simply half press the shutter to get the camera to focus on the subject, with either single or continuous focus. When you are happy with the focus, press-and-hold the back AF/MF button with your thumb. You have now locked the focus and the shutter button will only release the shutter. You can recompose and shoot as often as you like, the focus is locked. Release your thumb.to allow the shutter button to be used to set focus again.

Others do that as well but it isn't as intuitive or quick. Also, it doesn't give you the benefit of AF-C or whatever it's called in Sony cameras.

I believe Canon was the first to introduce this feature back in the 90s in the Canon Elan II/e/ (EOS 50/e, outside of America, and EOS 55 in Japan) It was custom function 4 setting 1. It assigned AF to the rear AE lock button. The button did not need to be held down. Press for AF and let go to lock. That is how I used my Elan IIe back then.

The whole point was to separate AF and AE from each other in the normal operation of the shutter button. You simply selected your focus point and it was locked and then you could concentrate on recomposition and exposure with the shutter button now only activating and holding exposure. Made shooting a joy.

The Canon Elan IIe was a joy to shoot with a lot of cool features. It had eye tracking AF and eye activated depth of field preview. Look at the little boxes in the view finder and AF points and depth of field preview activated!

I have the back button set to toggle between continuous and one shot AF. That way I can be in one shot until something starts moving and as soon as I press the back button my camera is tracking. It has improved my photography.

Joe Healey's picture

Thanks for this article. I cannot wait to shoot with this set up. But can anyone explain WHY the focus point does not reach all areas of the frame? That I've never understood.

you set up what your focus points will be. i use just the center focus because that's what works for me. others use something different. all it does is separate the focus and shutter release buttons so if you need to keep something in focus and recompose you can, think of it as focusing on second base in baseball, that is where the play will end up. now you can compose to follow the runner or fielders without losing focus on the base. (did that make sense ?)

Joe Healey's picture

I think what I'm missing is, for example, why does the camera not allow me to position a focus point to the very top edge of the frame? I shoot Nikon.

If I'm understanding you correctly then the answer would be that there are no focus points in those locations to begin with.

Joe Healey's picture

Exactly. If I'm I shooting a full body shot 2 x 3 portrait oriented, the highest focus point is about chest level. Makes for a lot of focus/recomp movement. Not sure if that's a Nikon thing or a price point thing.

I do agree that it is odd that you don't have focus points covering the entire field of view.

Ansel Spear's picture

...an over simplified description: viewfinder focus points are limited to the central section of the mirror due to optical limitations/falloff. Live view focusing (Nikon) is edge-to-edge because optics are not hindered by the mirror.

Joe Healey's picture

Thanks Ansel.

joe sharp's picture

Pentax users you camera has a AF button that works like this. No need to change anything just keep shooting.

This feature has been around since the film days. IIRC it was on the canon eos 3 I was using back in the film days and on Nikon D1 when I switched. Steve Simon wrote about this in 2016 and I was surprised back then that it was considered a "trick".

Nope, even before that. See my post above.

So why did it 20-25 years for people to suddenly discover and write about it?

Jason Vinson's picture

Because there are constant flow of new photographers that don't know about it.

Tam Nguyen's picture

I fail to see why this is still such a rave when you can already do this by half pressing the shutter, assuming your have continuous servo AF. Am I missing something?

The most obvious problem is that your focus point doesn't always coincide with proper exposure. When I lock focus with the rear AF button I can then focus on recomposition and proper exposure. It never made sense to have AF and AE on the shutter button.

Rex Jones's picture

I do the exact same thing. I have found that it ultimately gives me more control over the image as a whole. I do it 100% of the time with my landscape shots, but I have found it to be helpful with portraits as well.

I shoot like that 100% of the time. I'm not interested in action photography so all I need is a very sensitive and accurate central focusing point. I also spot meter most of the time.

Tam Nguyen's picture

I shoot mostly in manual so I guess it's a moot point for me.

Sanjay Gohil's picture

I must be one of the few that don't use BBF!

I've set up my Canon 5d4 to shoot in AiServo mode and I've programmed the 'DOF' button to switch to one shot when I press it. I can easily switch between my subjects moving and being still.

Maybe I'm over complicating things but I also use the small jog dial and 16 focus points to compose my shots, I guess muscle memory has got used to it.

Pawel Paoro Witkowski's picture

For me it seems same, I see no point in locking focus and then recomposing which add a dial of error in focus, especially on smaller apertures where millimetres matters. I'm using only selecting focus points and they work pretty damn well, and I see no real problem during shoot to select the one i'm really interest in.

I may be also one of the few that don't use it. Although I tried. But it bothers me that I have to recompose all the time if I wan't to have object at the side of frame. At f2 or f1,8 i am not sure if focus will hold.

Also, when setting to AF-C, what mode do I set it to? Single, 9 points...?