I have to admit, years ago when I first heard about back button autofocus, it took me a while to wrap my brain around. On the surface it looks like it complicates taking photos. You have to press one button to focus, and then another to release the camera shutter. This is in contrast to how most modern cameras work out of the box; the shutter button controls autofocus AND shutter release, essentially allowing you to just press one button to do everything. Like anything new, back button autofocus takes a little while to get used to, but I promise that after you do, the benefits will become apparent quickly.
3 Reasons to use Back Button Autofocus
Think of it as “intelligent” autofocus
For years before autofocus, photographers focused their lenses manually. This has the inherent advantage that the shutter was never attached to the focusing mechanism. So, you could focus on the subject and wait, and when you were ready to take the shot, just press the shutter. To me, back button autofocus is the best of both worlds! You get to use the excellent autofocus system of the camera to quickly lock your focus and then the moment you’re ready to snap the picture, you know you can just press the shutter without the camera attempting to refocus.
Great for fast moving objects entering and leaving a scene
With regular autofocus, if you want to “hold the focus” on something, you need to keep the shutter pressed halfway down. For instance, if you want to prefocus on an area and wait for the object to enter the scene, you’ll be holding your finger down halfway for a while. When you separate the focus and shutter, you can lock the focus and be sure that if something new enters the scene while you’re waiting to snap the photo, your autofocus won’t be thrown off.
Not every shot requires refocusing
Let’s say that you’re taking a series of portraits and you’ve focused on the subject’s eye. If you’re going to keep them in the same plane of focus, there’s no need to refocus on every single shot. Your thumb focuses using the back button and then you’re free to snap away without fear that the shutter button will refocus.
Setting up back button autofocus on the OM-D E-M5
1. Remove autofocus from the shutter button
Tap “Menu” on the back of the camera and access the gear menu on the left. From here select the “A” gear menu (AF/MF). Arrow down to the AEL/AFL settings, select S-AF (single shot autofocus) and then mode3. You can see that a half press will only lock in the exposure settings (AEL), and will not focus.
NOTE: You can also do this same procedure for C-AF above, if you’d like to do back button autofocus for continuous focus mode.
2. Assign the Fn1 button to autofocus
I’m sure the engineers at Olympus thought about this one, since by default, the Fn1 button is already assigned to AFL (autofocus lock). However if you may have played with the menus and buttons (like we all do!) at some point, then you may need to check or change the setting.
First, access the gear menu and the “B” Button/Dial menu, then Button Function.
This is a great menu, as you can change almost any button function on the camera. Specifically, we’re just going to verify or change the Fn1 button right now.
You’ll see that you can assign almost ANY function in the camera to the Fn1 button, but here we’re going to want to set it to AEL/AFL.
3. Test your settings
Make sure that when you half press the shutter you don’t hear or see any autofocus happening, and that when you press the Fn1 that autofocus engages. Also make sure that when you full press the shutter, your camera still takes a picture!
4. Save your settings
If you’re like me, you’re not going to want to use this setting 100% of the time. This is where the Myset settings on the Olympus OM-D cameras come in super handy. I assign back button autofocus to Myset4 in my camera so I can get to it quickly, when I need it. If you have an Olympus OM-D series camera and don’t know about saving your settings as Myset presets, check out the post I wrote about it here.
Do you use back button autofocus? Does it help you or do you think it just adds complication? Leave a comment and let me know!
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