Autofocus (AF) points appear in the viewfinder or LCD screen of most SLR and DSLR cameras, even a few point and shoot cameras use them. So what are they? AF points are designed to help you know where your camera is focusing and to let you refine where the camera actually focuses.
What is an Autofocus Point?
When using your camera in autofocus mode, the autofocus points will help you direct the focus to a particular location in the frame.
This is extremely convenient because the focus of your photo may not always be in the very center where the camera traditionally likes to focus and meter.
Autofocus points were introduced in film SLR cameras when the Canon EOS and Nikon F-series models were very popular. Since that time, the technology has moved into digital photography and is included in almost every DSLR as well as many point and shoot cameras.
The introduction of AF points gave photographers greater freedom in focusing on certain subjects in the photograph. It mimics the freedom of manual focus while giving you the smooth, quick operation of autofocus.
Autofocus points can also be connected to the camera's metering system in many models. This means that the camera will determine the appropriate exposure based on the chosen autofocus point, which is typically the photo's main subject.
The number of possible autofocus points depends on the camera.
Some cameras have a 9 point system, while other cameras have 11 points or even 51 points. The more AF points a camera has, the more options you have to fine-tune the focus.
What Do Autofocus Points Look Like?
Autofocus points are generally shown as small squares when you look through a camera's viewfinder or on the LCD screen.
Many models also include a set of brackets or a circle around the middle point.
When you press the camera shutter button halfway down to focus, the AF point(s) in use will light up. Red is a favorite color for camera manufacturers to use but some cameras have AF points that are green or another color.
How to Use the AF Points
There are a few ways to use your camera's AF points while taking a picture.
Allow the camera to choose the AF point for you. This is an option on many DSLR cameras and may be the only option for some point and shoot cameras. On DSLRs, you may have to enable (or disable) this setting if you do or do not want to use it (check your manual for instructions).
In this mode, when you press the shutter button to focus, the camera will automatically determine what your main subject is. This may be the largest object in the frame or the fastest moving, the camera's computer attempts to find the most important thing and will assume that this is where you want the focus.
Obviously, with all things automatic, this may not be exactly what you intended. For example, the camera may think you want to focus on the tree in the foreground when you really want the barn off to the side to be the sharpest object in the photo.
The camera cannot read your mind and that is why it's good to know how to change the AF point manually.
Choose the AF point yourself. If your camera allows it, you will find that this option is a far better use of the AF points because it gives you, the photographer, control over your images. You may be able to trust exposure to the camera, but the focus should be in your control.
Consult your camera manual to determine if you can manually select AF points and familiarize yourself with the button to initiate it. On Canon and Nikon DSLRs this is often a button on the back right of the camera (a task for the thumb on your right hand). When active, you can then toggle between AF points using the camera's arrow keys or one of the wheels (again, every model is slightly different).
Familiarizing yourself with this feature will improve your photographs tremendously.
You can choose to focus on a subject in the extreme foreground or background, to the far side or way up at the top (or bottom). The point is that you have control over the focus.
What Happens When the Camera Can't Focus?
No matter which method you use, if the camera cannot properly focus on the object behind the AF point, it will not allow you to take the picture.
The cause could be:
- The subject is too close and out of your lens' minimum focal range.
- The subject is too dark for the autofocus to work.
If you run into any of these issues, the camera will use an indicator to tell you that it cannot focus. Some models use a flashing light inside the viewfinder or on the LCD screen. Be sure to look in your manual so you aren't surprised when this happens (and you can't take a photo!).
When the camera cannot focus:
- Try selecting a different AF point that is close to your intended subject.
- Use the same AF point and move the camera slightly to the side until it does focus, then reframe your photo without lifting your finger off the shutter. (This trick can affect focus and exposure, so check the photo to see if it worked.)
- If you're focusing on a close subject, back up until you are behind the minimum focusing distance of the lens (this is often less than a foot). Zoom in or reframe the image to make the composition work again.
- Switch to manual focus, if available, and rely on your own eyes to get the image sharp.
AF Points and Moving Subjects
Many camera models have intuitive programs that sense motion and these can aid you when taking pictures of fast-moving objects like sports, kids, pets, and cars. Every camera is different, so play around with the settings until you become comfortable with them.
In some cases, the camera may allow you to choose a set of AF points and it will then choose the best one to use when the shutter is actually pressed. This is very convenient if you can predict where the motion is going in the frame.
For example, let's pretend that you're on the sidelines of your kid's soccer game and the players are coming down the field.
You can choose an AF point (or series of points) on the far side of the frame (where the kids will run out of the photo). As soon as the first kids are in this spot, click the shutter button and the camera (should) respond immediately by focusing the lens and snapping the picture.
Capturing motion with even the most advanced camera is tricky and takes practice. Take some time to figure out how best to do it with your camera and use the available AF point system to your advantage. You'll be stopping motion in no time.