In most of my previous PhotoFit columns I've been hitting on techniques to get the best exposures for your images - basically making sure your image is sharp. I've been throwing around the term "sharp" a lot, but what that really means is "in focus." Getting your images in focus is the name of the game. I can't reiterate more how critical focus is for an image. No matter how special of a moment that you catch, if it is out of focus, it's worthless. This column will focus on focus, and the secret way to get it: The almighty back button.
All DSLRs share many of the same hi-end focus systems - the most basic being full auto focus. That basically means the camera does the thinking and when you half-press the shutter, it guesses what should be focus and then it takes the image. Turn that off immediately.
Next up is Single Point (apologies, I speak Nikon, but Canon has all the same systems named slightly different). Single point gives you great focus on your center point (or whatever point you select), but it will not adjust if your subject moves forward or back before you hit the shutter. Not useful for fitness.
Nikon D600, Nikon 70-200, 1/500th, F2.8, ISO 6400
Now, let's talk about Continuous Focus. This is where your camera should live. Depending on the body you have, there will be a range of options from D-9 all the way to D-51 which refers to how many active focus points will be used to acquire focus. Quick tip, using less focus points actually helps the camera grab focus faster in most cases, so usually just pick something in the middle of the focus points your camera has.
So now here's the real inception mind-twisting moment. All cameras you've ever used have focus and shutter release connected. What if I told you they didn't have to be? Here's the magic of the back button. Right around where your right thumb naturally goes on the camera is a button named either "AF-ON" or "AF/AE-L" or something along those lines. Activating this button will de-link the shutter from focus. What does this mean? If you hit the shutter button the focus will not change and the picture will be taken whether it is in focus or not. The "back-button" now controls focus. Anytime you hit that button, your active focus point will try to grab focus. Whenever you stop hitting that button, the focus will remain locked on the camera. When you hit the shutter button, this image is taken.
Nikon D4, Sigma 35 1.4, 1/500th, F1.8, ISO 3200
What does all this mean and why is this incredible? Because you can finally keep a focus in focus during a snatch. You can grab perfect focus on a subject's head while they are doing pull-ups. You can nail focus over and over with predictable results that aren't skewed by your cameras overthinking focus computer.
To activate AF-ON each camera is a bit different but the basic steps (on a Nikon camera) are as follows. Go the Custom Settings Menu, select Autofocus. Go to Assign AF-ON button (or assign AE/AF-L) and select AF-ON. Also, you'll have to take a second step on most cameras and go to the AF Activation Menu and select "AF-ON" only. What that does is fully sever the connection between the shutter and the back button.
Back Button focus in action
So first off, using this will lead to a ton of out of focus pictures.... at first. There is a serious learning curve to understanding that cameras now have more than one button. The shutter button just takes images now. And it will do it whether you're in focus or not. You'll need to learn when to hit the back button and when not. You also need to feel out your lenses and know when they are in focus and not. Here's a great example: a kipping pull-up. Let's say we're lined up to the side of the pull up rig. I'm trying to get the subject's head perfectly in focus over the top of the bar. I don't want their hands to be in focus. Using a traditionally autofocus system linked to the shutter button, the camera would grab focus on the hand in front of the head, but not the subject's head (usually). With the back button active, I'm going to stay still and wait for the subject's head to get to the apex of the movement and hit the back button. I'm not going to take the photo though. I'm going to wait for the subject to hit the second pull-up and then hit the button. I'll repeat this process a few times. Over the course of a few reps I'll continue to lock the focus tighter and grab a few more shots. The image wouldn't ever come out in focus before (or would be total luck to get it).
Nikon D4, Tamron 24-70, 1/400th, F2.8, ISO 6400
Another great example -- the snatch. With an autofocus system, it will generally grab whatever is closest to the camera at any point in time. That will generally lead to focus on the hands, the barbell or anything else that jumps out. With the back button, I'll grab focus on the head during the setup position. Once the lift begins, I'll not hit the back button again and this will usually get me an awesome series of in focus images. Note though, if the head comes closer to me or farther away, there's the possibility depending on your aperture, the subject could slide out of the focus plane. In that case you'll need to hit that back button again and recompose.
Here's another great use of the back button: focus and recompose. So composition is always critical in an image. But generally you're working with the center focus point. With the back button - and if the subject is not moving farther from the camera or closer to it - I can set my focus, let go, and then recompose however I'd like and then hit the shutter. This might sound trivial, but when you realize how quickly you can get shots in camera with the composition and focus you want, your mind will soon be blown.
Nikon D600, Sigma 15 2.8, 1/500th, F2.8, ISO 3200
Cautions
Realize that you're now in control of the focus. If you don't hit the back button, the image will definitely be out of focus. But also, if a subject moves closer to the camera or farther away from the camera during a sequence, your perfectly in focus setup will lead to an out of focus catch position. This is where the real art comes in of knowing when to hit that magic button and when not to.
This takes a lot of practice to get the hang of, but gives you full control of your camera in an incredible way. Give it a try, learn it, love it. Comment below if you already use the back button or if you're trying it out now.
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