Focus Lock & Subject Tracking

Additionally you can choose single shot auto focus or focus tracking. Single shot (AF-S) focus can be locked by you. Continuous focus (AF-C or AI Servo) will attempt to track a moving subject and adjust focus as the subject moves.

In single shot (AF-S) focus mode you can lock focus by half pressing the shutter button, you will hear a beep and see a green focus confirmation dot in the viewfinder when you achieve this. You then fully press the shutter to take the photo. This is useful when you want to choose the focus point. If you are using single point autofocus you can place the focus point on your chosen subject, lock focus by half pressing the shutter button, and then you can recompose the photo to have your subject in focus but on the edge of the frame. The subject will stay in focus while you hold the shutter button, and the image will only be taken when you fully press the shutter. Single point and single shot (AF-S) autofocus modes make a good combination when you want to be in control of what is in focus when shooting static objects.

In AI Servo / AF-C autofocus mode, when you half press the shutter button, instead of locking focus, the camera will try to maintain focus on the subject even if it moves. This is a useful mode combined with auto area, if you are taking photos of subjects that are moving around a lot because you have a better chance of having your subject in focus even if they move closer or further from the camera.

Either of these focus modes can be used with each autofocus area mode.