A photographer can compose a beautiful image and then ruin it because of improper focus. Even with all the exposure settings perfectly in place for the surrounding environment, you may still end up with a blurry photograph.
This can cause a lot of frustration for photographers because this is something that cannot be fixed in post-editing.
Yes, some photographers prefer the blurred look to represent motion, but this type of blur is done on purpose. In order to avoid an accidental blur, autofocus comes into play.
There are three autofocus modes to choose from.
If your subject is stationary, this is the right AF mode to use.
With the shutter-release pressed half down, the camera will focus on the subject one time.
Until you take the picture, the camera will remain locked in focus.
This AF mode is best for action shots, when you know the subject will be moving. No matter where your subject moves within the frame, this AF mode will track it.
As long as you are panning along while the subject moves, the camera will continue to update.
Al Focus/Auto AF.
Not all cameras come with this third mode, but it can be the best one to use as it switches from one-shot to continuous automatically. Auto AF will detect whether the subject is stationary or moving and make adjustments accordingly.
When it comes to using autofocus, you not only need to know what mode to use, but what area mode to use. This is because autofocus modes only determine how the camera will focus, whereas area modes dictate where the camera will focus.
Here are the common area modes found on most cameras:
Single Point AF-Area Mode.
Depending where your subject is in the frame, you will choose one focus point. Wherever you select, the camera will only detect contrast in that given area. This works best when the subject is stationary.
Dynamic AF-Area Mode.
There is still only one focus point that is selected, but if the subject moves, the camera will utilize surrounding focus points to track the subject. This only works if the photographer pans the camera to keep the moving subject close to the initial focus point.
Auto Area-AF Mode.
The camera does the focus selection for you. It will take what it believes to be the subject in the photograph and blink the focus points back at you. If you agree, you can snap the picture with the subject in focus. This area mode is not for everyone, especially if you want control over the focus points of the image.
It can be frustrating when the camera keeps detecting something else in the image as your subject.
The autofocus system isn’t perfect, as is the case with all technology. In cases with low-lighting, it can be difficult for the camera to detect contrasts, as this is how autofocus works to obtain sharp images.
Once you are more comfortable with photography, you can practice with manual focus, but autofocus will help to get the image you want most of the time. You simply have to know what mode is right for the shot you are taking.