Canon PowerShot SX400 IS Black Manual (en)

Choose a subject to focus on.
Aim the camera so that [
] is 
on the desired subject, and then 
press the [ ] button.
When the subject is detected, 
the camera beeps and [
] is 
displayed. Even if the subject 
moves, the camera will continue 
to track the subject within a 
certain range.
If no subject is detected, [
] is 
To cancel tracking, press the [ ] 
button again.
Press the shutter button halfway. 
] changes to a blue [
], which 
follows the subject as the camera 
continues to adjust the focus and 
exposure (Servo AF) (
Press the shutter button all the 
way down to shoot.
Even after your shot, [
] is 
still displayed and the camera 
continues to track the subject.