Back button AF is one of the polarizing topics that keeps coming up. I used back button AF with my Canon DSLR cameras for many years, but since the launch of the EOS R, I’ve drifted away to the point of not using it at all. It is time to look at how you work with a modern mirrorless and determine if back button AF is necessary at all.
Back button AF is where the camera buttons are reconfigured so that the half-press of the shutter no longer initiates focus, but instead the photographer presses another separate button to actuate AF. Conventionally this was a means to avoid switching from one shot to Servo focus. Set the camera for Servo AF, then press and hold the back button to focus and track a moving subject, press and focus then release to be able to recompose a bit like one shot AF. With subject tracking in mirrorless cameras you can recompose while tracking a moving subject in the frame using Servo AF. So maybe back button AF is redundant.
Brian is a freelance photographer and photo tutor, based in Oxfordshire. He has unrivaled EOS DSLR knowledge, after working for Canon for over 15 years, and is on hand to answer all the EOS and photographic queries in Canon-centric magazine PhotoPlus.
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Since the Canon EOS-1D X and Canon EOS 7D Mark II it is possible to change AF settings as well as initiating focus with one or more of the custom buttons. I know photographers who use AF-ON for tracking a moving subject and AE-Lock for switching to 1-point AF for a stationary subject or activating eye tracking and focusing. So, in effect, it’s become more about using the back buttons to change the camera’s AF settings rather than choosing when it focuses. In this respect simply reconfigure the AF-ON button as an AF-OFF button to stop AF whenever it’s pressed. The surprising part is that there are a lot of photographers using mirrorless cameras as they’ve used DSLRs so they don’t allow the focus technology to help them, which is often the reason for switching to mirrorless.
The other benefit of not using back button AF is to customize buttons for other features that are more useful. To freeze a car travelling at speed you need a fast shutter speed, but then it turns a corner and you press a button to drop the shutter speed to something for panning on the same bend. It’s time to evaluate how to work smarter.
If this article was of interest you might also like to find out more about the best Canon cameras, along with the best Canon DSLR lenses or best Canon RF lenses for mirrorless bodies.
