Debunking Back Button Autofocus

Photography seems to go through trends. Camera clubs, and places like Flickr have at some point or the other, been overrun with examples of colour popping, HDR (more accurately, excessive tone mapping), and tilt-shifting (more accurately, tilting). But these trends aren’t always limited to image styles.

One thing which seems to have grabbed the imagination of many photographers is the use of a dedicated button on the back of the camera to autofocus, instead of activating it through a half-press of the shutter button, which is something that can be done in higher end cameras. Many photographers are now of the opinion that this is a better way of doing things. I don’t believe back button focus is inferior, but I certainly don’t think it is a better way of doing things either, aside from one caveat mentioned below.

I believe the trend started when a professional sports photographer or two proclaimed their love of this method, and like many things on the Internet, it soon became the “right” thing to do. I remember first learning about it some years ago and, despite being a professional sports photographer myself, being thoroughly flummoxed as to why people seemed to find this a preferable way of doing things. I still am!

As I understand it, the main advantage of decoupling autofocus from the shutter button is so that the photographer can leave the camera in continuous autofocus, yet still be able to focus and recompose (with the subject off centre) when necessary, by simply letting go of the AF-On button on the back of their camera.

So far, so good. Makes plenty of sense.

Except that my cameras have permanently been in continuous autofocus for over a decade, and I have never used the AF-On buttons to focus with, and I have been perfectly capable of locking focus and recomposing through the years. The “magic” simply comes from the AF-Lock button, or in my case, the AF-On button, that is configured to serve as a dedicated AF-Lock button instead.

Basically, I use the button exactly the opposite to how back button focusing works. Instead of having to press a second button to AF, I press a second button to not AF. On this level, which one works and/or is more convenient for you, depends on which you spend more time needing – autofocus, or no autofocus. Personally when I shoot sport, and wildlife, I find that I need autofocus more often than I don’t. Which means that I’d rather press an extra button on the occasions I don’t need it, than press it on the occasions I do.

Take sport. I estimate that generally I spend at least 90% of the time tracking a subject, and maybe 10% of the time (that’s generous) needing to lock focus and recompose a shot. Why press an extra button for 54 minutes in every hour, when I can just press it for 6 minutes?

I’d argue the percentage is slightly less skewed when shooting wildlife, although generally I still spend comfortably more time tracking animals than locking and recomposing. If you are camping a perch in a hide then back button focus could be useful, but if you are shooting active animals, then you need AF more often than not. Even for an animal on a perch, working with long lenses means depth of field is marginal enough that you periodically have to re-determine focus.

Yet it is apparently in sport and wildlife where switching to back button autofocus is most useful!

Other reasons for using back button focus that I have seen are:

  • Optical stabilisation systems do not engage when using the back button to autofocus, so you can track a subject and not waste battery having the stabilisation running while you are doing so.

First point is, if you are worried about battery life, then the answer is to buy a spare battery. In the grand scheme of things under normal usage, I’d be surprised if this saved you more than a couple of percentage points of power. If you’re in danger of running out of power, then you really should have a spare battery or two on hand. If you were in a car and running low on fuel, the real solution is to fill it up, rather than switching off the air conditioning.

More importantly, stabilisation systems need time to work, otherwise they can actually add blur to your pictures. So if you are using back button focus, and haven’t triggered stabilisation, and suddenly need to fire the shutter, then you might actually be compromising the sharpness of your image.

Which is possibly the reason that the latest high end Nikon cameras now also activate VR when using the back button to focus (the D4 and D800 onwards). Which then renders the battery saving argument totally moot.

Note for Nikon users: Generally speaking most action photography is done at high shutter speeds. VR should be switched off altogether at high shutter speeds, as you can end up with softness or additional shutter lag, as the Nikon VR element takes a moment to re-centre itself prior to exposure.

  • Avoiding accidentally triggering the shutter, when merely trying to track the subject.

With some skittish subjects, this can pose a problem. But while accidents can and do happen, the solution to this one is to be comfortable enough with your camera so that it doesn’t happen. Most “accidental” shutter actuations seem to come with high frame rate cameras and firing off more frames than intended, as opposed to firing when not intending to fire. In other words, the challenge is stopping the shutter in time, rather than accidental activation.

I would also argue that having to juggle pressing two buttons, makes you similarly liable to you accidentally firing the shutter when you only intended to get ready to shoot. Good shot discipline means that you really shouldn’t be stabbing at the shutter in one motion anyway, so being “ready” with a half press is good practice.

Reasons I would suggest that shutter button focus is better:

None of these are particularly major reasons, but I’ll point them out anyway.

  • Long days in the field can result in weary shutter fingers. Having to press the AF-On button as well for an extended duration just adds to that.

I’ve actually seen an argument that AF-On allows the index finger to relax during a long day in the field. Yet if you are shooting action, then your index finger really should be “ready” whether you are using back button focus or not. As mentioned above, proper shutter discipline means you should never be stabbing the shutter, and to react quickly your finger should be ready to go anyway. So really, with back button focus all you are doing is… adding your thumb to the list of things that gets tired.

  • Your reactions are ever so slightly faster, as you only have to worry about pressing one button, instead of pressing two buttons in a 1-2 sequence (as the AF-On button has to be activated before you can fully depress the shutter button).

With shutter focus and AF-Lock, when you have to activate two buttons, you are already losing a fair bit of time and an extra split second doesn’t generally matter.

However for when you need to point at something quickly and shoot as fast as possible to capture the moment, then I’d rather be as efficient as possible. With shutter button focus, you… [1] point, [2] half press the shutter button, and [3] take the picture. With back button focus you… [1] point, [2] press the AF-On button, [3] half press the shutter button, and [4] take the picture. We are talking very fine margins, which is why I’m not trying to suggest that back button focus is inferior, but it’s certainly not better in this situation.

  • If you are using a camera that doesn’t activate optical stabilisation with the back button, then you can end up with slightly blurred images if you have to react quickly.

Although as stated above, the newer high end Nikons have taken care of this problem, albeit at the same time removing one of the supposed reasons to use back button focusing. Clearly Nikon think that it’s more important not to ruin the image with a dormant VR system, than saving a bit of battery life.

Notice that both the latter points in favour of shutter button focus are concentrated on responding quickly to action… precisely the area where back button focus is supposed to be “better”.

The caveat:

I have found one reason to use back button autofocus – it makes it a lot easier to use autofocus when doing landscape work on a tripod, for example with 10 stop filters. However I prefer to be in manual focus when doing landscape work to begin with, and really this is not an area where back button focus is supposed to be “better”.

The poser:

Just a cheeky question for you to mull over: If back button focus is so good, why not back button metering?

The conclusion:

Ultimately neither technique is wrong, or inherently worse, but I find it perplexing that photographers have become enamoured with back button focusing. It is significantly better than having your camera in AF-Single or One-Shot AF, but I’d never have the camera in those modes to begin with!

  • Share

11 Responses

  1. Thank you, Thank you!! I’ve been thinking I’m going out of my mind trying to explain to people why BBF is pointless, and you’ve explained it so succinctly better than I ever could. Thank you

    • Thanks Mark – sometimes it seems an uphill struggle when everyone else is saying something to the contrary. When the Internet gets an idea sometimes it’s very hard to stop the juggernaut!

      I’m a member of various photographic groups online and on social media, and there are a huge number of people who say “I tried BBF and I could never go back now”; which just ends up propagating the situation. There’s nothing inherently wrong with BBF, but there’s certainly nothing inherently better about it either!

  2. I got a new camera which is a major step up from my previous one. I have been taking much worse shots since I have started using the back button focusing with my sports photography.

    Now going to shut it off and go back to the shutter shooting.

    • Back button focus takes a while to get used to, and for certain things it can be advantageous; but as outlined in the article I honestly believe in the majority of situations traditional focusing is at least as good. Good luck!

  3. Anyway you look at it BBF gives you more time looking through the view finder with less to distract you from the the primary objective; a well composed and exposed image. It’s that simple, that’s why its appealing, Eye to viewfinder, go.

    Yes it’s personal preference but the functionality of this method cannot be denied, it has validity and merit for many photography subjects and when you acquire the muscle memory going back to the old system seems a retrograde step.

    That said I’m using a Nikon D5500 and I’d say until you’ve tried all the functionality on that particular model fully set up and programmed for Back Button focus by Steven Simon Street Photographer
    (Lynda.com – Performance Tuning the Nikon D5500) you might not have experienced the full power of this style of usage. The D5500 was made for this, it’s fully BBF integrated unlike many other cameras and fully complimented by a touch screen that you can even use as part of this bbf system while looking through the viewfinder, again enhancing functionality without taking your eye of the subject.
    If youre only talking of that one button then sure it’s no big deal but it’s not just that one button, it’s an entire system on the D5500, its easy, fast and dependable and and cuts the overhead stress load when your busy and delivers 100% of the time.

    • Unfortunately that appears to be a registration site, so I cannot review the article you mentioned. As mentioned in my post, there is nothing drastically inferior about BBF, but similarly in my own experience there is nothing inherently superior about it either. Ultimately picking the best method comes down to you and what you shoot, but I personally disagree with the whole “BBF is so much better” mantra that seems to be doing the rounds.

  4. Amazing. this whole BBF drama is nothing but another form of BS herd behavior and “me too” mentality. I used to shoot action just fine with the normal focusing practice. I tried this must have BBF and found it useless and pointless. Simply another button to press and miss the shot

    • I agree Wesam, there are quite a few photographic subjects that the Internet has propagated that don’t necessarily pass muster when examined closely!

  5. Re: your comment “Your reactions are ever so slightly faster, as you only have to worry about pressing one button, instead of pressing two buttons in a 1-2 sequence (as the AF-On button has to be activated before you can fully depress the shutter button).
    I have a budget Canon DSLR EOS 1300D and i can press the shutter button at anytime whether the subject is in or out of focus when i use back button method, When using the shutter button i have to wait till the camera descides it has “got focus”. I use both methods neither is better than the other. Just pointing out you can take the picture at any point using the back button method. There have been times when the unexpected happened and i just picked up my camera pressed the back button to start focus and shot away with out waiting for the auto focus to tell me it had attained focus and let me press the shutter. A few blurry shots yes but i captured the important one too !!

    • Hi Richard,

      Thank you for your comment. You are correct in that it is important to make sure you get the shot, even if it means a few blurry shots.

      I should perhaps clarify the statement that you’ve quoted – I never meant to imply that you couldn’t fire the shutter without pressing the AF-On button. What I meant was in order to activate autofocus, you have to press the two buttons in a 1-2 sequence.

      Additionally, you should be able to set up the situation you’ve described even without back button focus with higher end cameras. You can select shutter button release priority or focus priority with Nikon cameras for example, so the shutter will fire even when the subject is out of focus.

Leave a reply

Your email address will not be published. Required fields are marked *