Canon IXUS 310 HS - Manual (Page 79)

Detecting a Face and Shooting (Smart Shutter)
79
Join the subjects and look at the
camera.
X When the camera detects a new face, the
lamp and self-timer sound will speed up
(the lamp remains lit when the flash will
fire), and two seconds later the shutter will
release.
z To cancel shooting with the timer after
countdown has started, touch the screen.
Changing the number of shots
After touching in the screen in Step 1, touch op to change the number of
shots, then touch Ú to complete the setting.
Even if your face is not detected after joining the subjects, the shutter will
release approximately 15 seconds later.