Focus tracking

Started 1 month ago | Questions thread
John_A_G Veteran Member • Posts: 7,816
back button focus

DavidWright2010 wrote:

Yes, I've come to the same realization.

When the next bird comes by I will try AF.C mode, TAv , and back-button focusing, and see what happens.


David - I think people suggest back button focus without understanding what it does and doesn't do.  It will have zero impact on the camera's ability to track a moving subject.

It can be very useful when you're WAITING for action at a given point.  When in AF-C with focus controlled by the shutter button - when you press the shutter button the camera will start to focus.  If you're waiting for a bird to take off (without the need to track AFTER it takes off) if you have focus control on the shutter button and you take your finger off while you wait - when you see the bird take off and press the shutter the camera will focus again - maybe you've moved it and it focuses on the wrong thing.

With back button focus, you can focus with your thumb on the bird, take your thumb off and wait.  When the moment comes you press the shutter with your finger and the camera won't re-focus.

Then, should you want to start tracking you can simply push back button with your thumb.  Push back button with thumb early and you have same risk - camera will refocus (maybe you've moved point and it focuses on the wrong thing).

So, back button focus can be useful in very limited circumstances.  HOWEVER, if you want to use it I suggest you keep it on all the time so you build up muscle memory and don't get confused over whether to use finger or thumb for focusing.  But, just make sure you understand what the feature does and doesn't do.

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