Canon POWERSHOT SX150 IS User Manual page 83

Changing the AF Frame Mode
Recompose.
Keep the shutter button pressed halfway
and move the camera to recompose the
scene.
Shoot.
Press the shutter button fully.
Detects people's faces and sets the focus, exposure (evaluative metering
only) and white balance (AWBonly).
When the camera is pointed at subjects, a white frame appears on the face
the camera judges to be the main subject, and gray frames (max. 2) will
appear on other faces.
A frame will follow a moving subject within a certain range.
When the shutter button is pressed halfway, up to 9 green frames will
appear on faces that the camera focuses on.
_ Tracking AF
You can choose the subject you want to focus on and shoot (p. 84).
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