Programming back-button focus on my a7ii and a6300 – it’s something I should have done a long time ago. Why didn’t I? Fear! It’s always fear. Fear that in the heat of the moment I’d forget that my shutter button no longer activated the autofocus.
But I was getting frustrated, and I’m sure you’ve had similar experiences.
For example, I was shooting some rare birds on the side of a riverbank from a moving boat in Costa Rica. I was using a very fast aperture at 300mm so focus was critical. Most of these shots were trash because of bad focus. I was using a small spot for accuracy and centering my subject. But because the boat was bouncing, and there were so many blades of grass at all focal planes, every press of the shutter was a roll of the dice. Sure, I could have used manual focus but time was of the essence here. And trying to hold a half-press on the shutter to lock the focus wasn’t working with the movement of the boat – I’d click when I didn’t want to or accidentally release and have to start all over.
How do we fix this? Setting what’s called back-button focus. Almost all DSLRs and mirrorless cameras have this feature. Here we’ll talk about how to program back-button focus on a Sony a7ii.
Back-button focus in a nutshell
Using a centered spot focus point, point your camera at your subject and press the assigned button on the back of the camera. Focus is set. Now, recompose to your heart’s delight without worrying about holding a half-press to lock focus or refocusing with each composition. Only valid when distance between you & the subject remains fixed.
Advantages of back-button focus
- Quickly & accurately set your focus and then change compositions without worrying about refocusing every time you take your finger off the shutter.
- If you spend a lot of time moving the Flexible Spot between each composition change to hold your focus point over your subject, those days are over.
- Becomes very powerful when combined with Continuous AF for moving subjects – always keep your subject in focus without doing the “half-press” dance.
- Works great in low-light & low-contrast situations – if you can set the focus once, AF will no longer “focus hunt” every time you half-press the shutter.
- Control, control, control – leave less of the decision-making up to the camera.
- And finally – just use the shutter button for the shutter!
Disadvantages of back-button focus
- Yes you’ll probably forget about this at first when you make the switch, especially if you’ve been using the half-press method for decades.
- Depending on how you want to program the switch you’ll lose Auto Exposure Lock (that’s not a feature I use so it doesn’t matter to me).
- The “set and forget” nature of back-button focus is only good when the distance between you and your subject is fixed – you’ll have to remember to refocus when distance changes, especially at wide-open apertures.
Programming back-button focus on the Sony Alphas
This customization is primarily aimed at the Sony a6300 & up, and the photos are an a7ii. You can reprogram the AEL button on the back of the Sony a6000 for this feature using similar steps as below. You could also potentially use the Center Button on the a5100 but the ergonomics of that may not be comfortable – I haven’t tried it.
We’re going to assign back-button focus to the little center button on the AF/AEL switch, and it matters if that switch is up or down. This is where the ergonomics of this function will be most comfortable.
You’ll start by going into the Custom Settings menu (the little gear icon under Menu).
1. Turn off Pre-AF
This is located on Page 3 of the a7ii Custom Settings menu. Pre-AF is like a continuous autofocus that tries to keep your subject kinda focused at all times, even when you’re not pressing the shutter. This defeats the purpose of back-button focusing.
2. Disengage the shutter button
On the next page, turn off AF w/ Shutter. We want to separate that shutter button from the focus!
3. Set back-button focus
Go to your Custom Key Settings…
And assign AF On to either AEL Button or AF/MF Button. I’ve assigned the AF/MF button to toggle between those modes, so I’ve assigned Autofocus to the AEL Button. This means that when I slide that switch to AEL and press the little button, it’ll activate AF. When I slide that switch up to AF/MF and press the button, it’ll toggle between Auto Focus & Manual Focus.
4. Customize other buttons
For now I’ve assigned other focus features to the custom buttons.
- C1 allows me to switch between focus modes (single shot, continuous, etc) but I’ve found I mostly just leave this in AF-C now that I use back-button focus. Continuous focus is always available if I need it, but I can also use it like single-shot AF with this.
- C2 adjusts the settings for whatever focus mode/area I’m in.
- C3 allows me to switch focus areas, but I mostly just leave it on Centered Flexible Spot now.
- Eye AF is a nice feature with the new Sonys – it detects your subject’s eye and focuses on it. It works fairly well.
5. Practice, practice, practice
You’ll need to reset your muscle memory now! Go out and shoot around before you have an important gig – you won’t want to forget about this reassignment when it matters!
Finally, back-button focus isn’t for everyone and it won’t work in every situation. But for those who need versatility, it’s a great option. Hopefully, when you get the hang of it, you’ll wonder why you never did this sooner.