By default, most DSLR (and all point and shoot) have the focus and shutter assigned to the same camera button. This is how most people learn to shoot: half-press the button to focus then press completely to take the picture.

While a lot of people use this configuration, many pros prefer to separate these features on two buttons for the following reasons (it is also called “back button focus”):

  • Once the focus is set, there are no risks of accidentally changing the focus point when taking taking another shoot.
  • Pictures can be taken faster since the camera does not have to wonder if it should focus or not, it simply take the picture.
  • When shooting in AI Servo mode, you can keep the camera focusing while taking picture, ensuring better focus.

It takes a bit of time to get used to it (1-3 days) but it is worth it, you will quickly wonder how you ever managed to shoot the old way.

Some additional reading:

Canon EOS 5D Mark III – Tutorial Back Button AF:

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