Best Click

By default, most cameras will autofocus when you half-press the shutter button. Although this is a nice feature, there are times when you will want the two actions – focusing, and taking a photo – to be separate from one another. Most cameras let you do this by assigning focus to a different button, often called AF-On, and removing it from the shutter release button. This is also called “back-button focusing.”

AF-On is exactly like half-pressing the shutter release, but it’s just in a different location. That might not sound like a big deal, but there are plenty of situations where you won’t want the camera to refocus when you press the shutter release, so AF-On is a crucial feature. We recommend that you use it instead of the shutter button if at all possible. There are practically no negatives and several potential positives.