How to Change the AF (Autofocus) Mode on the Canon Rebel 5/1200D
The other autofocusing option on the Canon Rebel 5/1200D you can control in the P, Tv, Av, and M modes is the Autofocus (AF) mode, which determines if and when the camera locks focus. You have the following choices:
One Shot: In this mode, which is geared to shooting stationary subjects, the camera locks focus when you press the shutter button halfway. Focus remains locked as long as you hold the shutter button at that halfway position.
AI Servo: In this mode (the AI stands for artificial intelligence), the camera adjusts focus continually as needed from when you press the shutter button halfway to the time you take the picture. This mode is designed to make focusing on moving subjects easier.
For AI Servo to work properly, you must reframe as needed to keep your subject under the active focus point if you’re working in Manual AF Point Selection mode. If the camera is set to Automatic AF Point Selection, the camera initially bases focus on the center focus point.
If the subject moves away from the point, focus should still be okay as long as you keep the subject within the area covered by one of the other nine focus points.
In either case, the green focus dot in the viewfinder blinks rapidly if the camera isn’t tracking focus successfully. If all is going well, the focus dot doesn’t light up, nor do you hear the beep that normally sounds when focus is achieved. (You can hear the autofocus motor whirring a little when the camera adjusts focus.)
AI Focus: This mode automatically switches the camera from One Shot to AI Servo as needed. When you first press the shutter button halfway, focus is locked on the active focus point (or points), as usual in One Shot mode. But if the subject moves, the camera shifts into AI Servo mode and adjusts focus as it thinks is warranted.
One way to remember which mode is which: For still subjects, you only need one shot at setting focus. For moving subjects, think of a tennis or volleyball player serving the ball — so AI Servo for action shots.
The Shooting Settings screen displays the current AF Mode setting in the area labeled in the figure below. To change the setting, you have two choices:
AF mode button (right cross key): Your fastest move is to press this button, labeled in the figure below. It takes you directly to the screen shown in the figure.
Quick Control screen: After activating the Quick Control screen, highlight the AF mode setting .The selected AF mode setting appears at the bottom of the screen. Rotate the Main dial to cycle through the three mode options. Or press Set to access the same selection screen you see in the figure above.