1: You can focus at one location and obtain AE lock at another location in the scene. Press the <*> button to autofocus and press the shutter button halfway to attain AE lock.

2: In the AI Servo AF mode, you can press the <*> button to stop the AF operation momentarily. This prevents the AF from being thrown off by any obstacle passing between the camera and subject. The exposure is set at the moment the picture is taken.

3: This is useful for subjects which keep moving and stopping repeatedly. In the AI Servo AF mode, you can press the <*> button to start or stop the AI Servo AF operation. The exposure is set at the moment the picture is taken. Thus, the focusing and exposure will always be at the optimum point as you wait for the decisive moment.