Even though a camera has an autofocus, it still needs some direction from the photographer to make sure it’s focusing on the right part of the image. The autofocus might be correct for one shot and then the next photo it might lock onto something in the background. You could always eliminate this problem by using the manual focus, but autofocus is ideal when you want to capture a landscape and focus on a specific spot in the image.
There are a few ways to get the autofocus to behave for you. Pressing the shutter half-way down to activate the autofocus and then recomposing can help. You can do this by setting the point of the autofocus to the center spot.
When you’ve done this you can point the spot to where you want to focus in the scene then press the shutter half-way down to activate the autofocus. When the button’s being held down, you can recompose the image and then push the shutter all the way to take the photo.
You can also use the autofocus and once it is locked onto the right spot, you can switch it over to manual focus. This usually works pretty well if the camera’s on a tripod and you plan on taking several shots from the same location.
The auto focus will kick in when you press the shutter, but there’s also something known as back-button auto focus. In this case you have to activate a button which is located on the camera’s back.
All you need to do is set the autofocus point at the center spot and then point it to where you want it to focus. Then you will press the button on the back of the camera to have it focus automatically on that point. The camera will be focused for all photos you’re taking from that position.
The same thing can be done by switching the camera to manual focus, but the back button means you don’t have to keep switching between auto and manual focus. The back-button method is ideal for moving subjects. If you hold down the back button instead of the shutter button, it means you won’t accidentally push the shutter all the way down.
The back-button often goes by other names on some cameras. This means you’ll have to read the manual to locate it as it’s a custom function.