Better Focus with Back Button?

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Today’s Question: I was at a camera club meeting last week and the presenter said we should always use back-button focus because it works differently than half-depressing the shutter release and results in sharper focus. I’ve always seen BBF as simply a convenience not something different technically that gives better results. Am I missing something?

Tim’s Quick Answer: With all cameras I am familiar with, the back-button focus option makes use of the exact same autofocus settings as focusing with the shutter release button, so either will result in the same sharpness for your photos. You decision of which approach to use should be based purely on which method best meets your photographic needs.

More Detail: Back-button focus refers to an option available on many cameras, where you can use a button on the back of the camera to activate autofocus. In other words, this enables you to separate the functions of focusing and capturing the photo. As a general rule, I recommend using back-button focus because it enables you recompose to take a picture without altering the autofocus setting.

If you use back-button focus (and have disabled focus for the shutter release button), I then recommend setting your camera to continuous autofocus. Then, to focus continually you press and hold the button for back-button focus. If you want the equivalent of “one shot” autofocus, you can press the button for back-button autofocus until focus is established, and then release the button to effectively lock the focus setting.

When you release the button for back-button focus with the process outlined above, pressing the shutter release button to check exposure or capture a photo will not cause the focus setting to change.

Of course, you may prefer having autofocus enabled for the shutter release button, and if that works for your needs it is perfectly fine. There is no need to choose one over the other to ensure better autofocus quality, as both will employ the same camera settings and features for establishing autofocus.