A focus mode where the camera continually refocuses on a moving subject. The more advanced the AF system, the better it will be at keeping the subject in focus. It’s used mostly in continuous shooting mode for sports and action photography but can also be used for video.
Almost all modern cameras have an autofocus system, where the camera automatically focuses the lens on a subject in the picture. They do this with multiple focus points arranged around the frame. You can choose the focus point you want the camera to use, or you can let the camera choose the focus point automatically – it will usually choose the subject nearest the camera. Here are some more articles about autofocus, the different technologies used and how to get the best results.
Here, the camera focuses once when you half-press the shutter release then holds that focus point until you press the button the rest of the way to take the picture. This is the usual mode for taking one photograph at a time (as opposed to continuous shooting).
Here, the camera tracks subject in continuous autofocus mode and uses its movement within the frame and any changes in its distance from the camera to work where it’s going to be at the moment the shutter fires.
An autofocus system that checks the position of objects from two angles. If they don’t line up the object is out of focus – and the system can use the difference to work out how far to refocus the lens and in which direction. Phase detection AF sensors are used on DSLRs and now phase detection pixels are built into some mirrorless camera sensors.
Useful when you want to make the most of depth of field – with often means focusing between two objects rather than on one or the other. It’s also handy for ‘zone focusing’ in shoot-from-the-hip style street photography, where you want an instant shutter response.