Updated: Oct 24, 2022
If you want to shoot scenes and people that are constantly moving and changing, it’s helpful to focus and capture your shots using separate buttons on your camera. The common way of doing this is called “back button focusing”.
Your camera is probably delivered with the focusing and metering done as you “half press’ the shutter button.
Search your camera’s menus for the “custom controls” selection or something similar.
On my Canon cameras the “AF ON” button on the back initiates the auto focus function. The customizing I did was to change the function of the shutter button from both metering and focusing to just metering. If your camera won’t let you do that, get a different camera.
When I shoot, I initiate focusing on a point in the scene that should give me good focus on the subjects I’m shooting. I keep that focusing indicator in the middle of my viewfinder screen because using the AF ON button means I can point the camera at the focal point I want, focus, and then frame the shot and shoot using the shutter button. If your shutter button is doing both functions, you’ll refocus the shot as you press the shutter button and you may find the focal point has shifted to something beyond your subject or in front of it. I find that using the back button technique is easier than maintaining that half-press on the shutter button while framing the shot.
If you’re new to back button focusing it will take some practice but, once you do it by habit, it will make your results much more satisfactory.