Canon 970 IS - Manual (Page 166)

164
Using the Button
1
In playback mode, press the button.
• This will call up the registered function.
z When you press the button in shooting mode, it switches
the camera to playback mode. Then when it is pressed a
second time, the registered function is called up.
z Registering a function other than to the button
disables its ability to turn off the camera power.