This particular article is related only to DSLR cameras and their Mirrorless equivalent - as far as I know, Back Button Autofocus isn't available on compact or bridge cameras which is a great shame as it's an extremely handy feature, but one which, sadly, is restricted to DSLRs for no good reason I can think of to be honest.
Like most things camera related, any change from the "default" norm can be quite daunting for a beginner. I know this coz I've been there. It takes a long time to get used to the many features on a digital camera and on a DSLR in particular, if you are tackling Manual Mode for the first time, just remembering your exposure triangle and thinking through what you're doing takes time. When the pressure is on - when you've got the perfect shot in front of you and you know you're time limited all the settings you think you know can suddenly fall out of your head and suddenly you're fumbling and panicking with dials and menus. Yes, it happens to the best of us.
The thing is though, this is all part of the learning process and with lots of time and lots of practise those settings become muscle memory and you just know what to do. But it does take a long time. And it does take a lot of practise. And it's perfectly understandable that you get frustrated from time to time because you are going to miss shots, and you are going to mess things up. You will get disheartened and, worst case scenario, you might just hang the camera up and say it's not for you.
So what the hell does all that have to do with back button autofocus? Well, it's yet another camera setting to add to the mix, and yet another "change" from the normal process of taking a picture that's significant enough to cause you problems initially but, well, I think it's worth it, primarily because it finally dawned on me that the normal way of autofocusing my camera was causing me problems. Let me explain.
The normal way to autofocus a digital camera is to half press the shutter button. When you do this you send a signal to the camera and it will either use it's phase detect sensor or it's contrast detect system to automatically focus the image in front of you. You then fully press the shutter button and the picture is taken. Couldn't be simpler.
But say you want to take another photo of the exact same scene? If you haven't moved and your subject hasn't moved, is it necessary to auto-focus again? Remember whichever method of autofocus your camera uses it takes some time to obtain and wouldn't you rather be thinking about your composition than on getting the camera to focus on exactly the same thing a second time with yet another half press on the shutter button? This is where back button autofocus comes to the rescue.
If you are using a DSLR (or Mirrorless equivalent) there will be a setting buried somewhere in your cameras menus that has some gibberish like:
Assign AE-L/AF-L button or worse:
C.Fn IV-1
You will have to check your camera manual for the specific setting for your camera but which ever brand and model of DSLR (or mirrorless equivalent - yes, it's getting very tedious having to specify that) you have it will very likely be there, in unintelligible hieroglyphs which mean nothing to any normal person.
Activating this setting (when you eventually divine where it is) will stop your shutter button from autofocusing so this means that half press will do nothing at all. Instead, one of the buttons on the back of your camera will take up autofocus duties. Now, on some cameras you can specify which button that will be. On others, it's just automatically assigned to a particular button, so once again you will need to check your camera manual to find out (or search the internet - somebody somewhere will have posted a video of how to do it with your camera). And now to autofocus, you press that button - hold it in until the camera focuses, and when it does it will stay focused at that distance until you press it again. This way the only thing the shutter button does now is take the picture and you can keep taking pictures for as long as you like without having to refocus every time. Take my word for it, if there's one change you can make to speed things up, this is it.
I moved to back button autofocus after about a year of using my camera in manual mode. I was frustrated by the camera focusing every time I pressed the shutter button and it was this frustration that made me look into the whole back button focus idea. Now that I'm using it I'll never go back to the normal focus method but it does take time to get used to it. I'm so conditioned to the half-press shutter button routine that I still forget I've moved to back-button focus and there are moments where I'm wondering why the hell the camera isn't focusing before it dawns on me so yeah, there's that, but with lots more time and lots more practise it'll become habit, like everything else. I have to keep reminding myself that you don't become an expert overnight; that it does, literally, take years and years to become accomplished, to worry less about what the camera is doing and concentrate more on what really matters: subject, lighting and composition. But if it were easy, everyone would be doing it. I'm a long, long way from being either accomplished or an expert. My pictures are better than they've ever been, but I would be a fool if I thought they were in the same league as the professionals. However, I'm not in competition with anyone, I'm learning all of this in my own time at my own pace and for the love of it, and that's pretty much contentment right there.
