What's autofocus and how does it work?
What's autofocus?
Autofocus means automatic focus, and it's often abbreviated as AF. It's a system your camera uses to automatically focus on a subject. A camera can automatically focus on a large or small part of the image that you see via the viewfinder or the screen.
How exactly does it work?
The best thing to compare autofocus with, is the eye. Just like your eyes, your camera works with contrasts in the image to ensure everything is sharp. When the contrast is highest, the camera knows that the image is sharp. Your camera determines which parts it has to focus on with a number of focus points. The total number of focus points depends on the model or camera type you have.
When do you use autofocus?
Autofocus is an easy way to quickly make your image sharp. Most cameras do this very accurately and fast. So you can be sure your photo comes out sharp. You can also use autofocus if you want to determine which part of the screen should be sharp yourself. You can move the focus points or single focus point manually. That's useful if you want a small part of the image to be sharp and the rest to be blurry.
Which autofocus settings are there?
With most cameras, you can choose from multiple autofocus settings. These are the most common autofocus settings:
- AF-S (Nikon) / One shot (Canon): in this setting, the camera focuses on 1 specific spot. Even if the subject moves, this remains the focus point.
- AF-C (Nikon) / AI servo (Nikon): in this setting, the camera focuses on 1 subject. Even if the subject moves, the camera stays focused on it.
- AF-A (Nikon) / AI focus (Canon): in this setting, the camera chooses 1 of the 2 autofocus settings mentioned above. This is based on the situation at hand.
What else should you know?
Autofocus isn't a holy grail. The autofocus system doesn't work as well in every situation. If there's little contrast between the subject and the background, it's difficult for the camera to focus, for example. And if you're too close to the subject, the camera can't focus properly on the right part of the image. In situations like these, use the manual focus option. You can manually focus with the lens ring.
