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Why I Switched to Back-Button Focus for my Sony Alphas

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Programming back-button focus on my a7II and a6300 – it’s something I should have done a long time ago.  But I didn’t because I was afraid that in the heat of the moment I’d forget that my shutter button no longer activated the autofocus.  Silly fears.

I was getting frustrated though, and I’m sure you’ve had similar experiences.  Sometimes manual focus was just taking too long, and in other situations, I didn’t have enough control over autofocus in dynamic situations.

How do we fix this? Setting what’s called back-button autofocus.  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.  The 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 the 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 on your subject, those days are over.
  • Becomes very powerful when combined with Continuous AF for moving subjects.
  • 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 – the shutter button is just for the shutter.

Disadvantages of back-button focus

  • It can take some time to reprogram your muscle memory.
  • Depending on how you want to program the switch you’ll lose Auto Exposure Lock.
  • 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 description 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.

AF AEL button

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.

PreAF

2. Disengage the shutter button

On the next page, turn off AF w/ Shutter.  We want to separate that shutter button from the focus!

AFShutter
3. Set back-button focus

Go to your Custom Key Settings…

Custom key

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.

AF On
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.

Custom buttons

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.

Alex Grover

Wednesday 27th of March 2019

One issue I have with back-button focus on that button is that when the image review pops up after taking a photo, that button becomes the zoom in button which stops the review image from disappearing and blocks you from taking another photo. Really frustrating in (for example) a situation when someone's walking towards you and you want AF-C to continue working and take a few photos. I could turn off image review but that doesn't feel like an ideal solution for me. Anyone else figure this out?

John Peltier

Wednesday 27th of March 2019

I think if you break it down into "wants" and "needs", you might find that you don't "need" auto-review enabled? There's always that playback button. It may be an important part of your workflow, but I've always found it distracting, and it consumes the battery much faster. Just my two cents. Cheers.

Monte

Wednesday 27th of June 2018

Does using back button focus achieve what is called, "pre-focus"? I understand that the Sony A7rii shutter lag in manual focus is about 100 ms while it is only 20 ms in "pre-focus" mode. Two days of google searches have produced no clear answer as to how to achieve this "pre-focus" mode to attain this short 20 ms lag time. I'm trying to use the A7Rii with a Lightning Trigger but due to excessive shutter lag it always captures dark sky after the lightning has gone.

John Peltier

Thursday 28th of June 2018

Hi Monte, the short answer is that I unfortunately don't have a definitive answer for you. It's probably something that only someone from Sony could set straight. But here are my thoughts on it. Back-button focus is how photographers pre-focus while in AF mode. You can also pre-focus in MF mode just by turning the ring. MF is pre-focus (as long as your subject is in focus!). But there's also Pre-AF mode. This tries to keep the subject in focus all the time so that your lens elements don't have to move around to focus when you press the shutter. I'm inclined to think that back-button focus will give you the longer lag. You're always pre-focused in MF mode as far as the camera is concerned, and it gives you the longer lag. The camera performs no focus functions when you press the shutter when using back-button focus either. Pre-AF is supposed to reduce your time from shutter press to capture, hence why I would think that's where the shorter lag is. So there may or may not just be a confusion of words with "pre-focus" and "pre-autofocus" when people discuss lag times. Wish I had a "yes" or "no" for you!

Hedy

Tuesday 6th of February 2018

Interesting... gonna try it for sure. One thing though, what if you need the metering and back-button at the same time? Is that possible?

John Peltier

Tuesday 6th of February 2018

You mean to use auto exposure lock? Yes that's possible. You can program the AF/MF toggle for AF On (that's now your focus switch) and the AEL toggle for exposure lock. I just used AEL for autofocus because I never use exposure lock. The nice thing about these cameras is having so many customization options!