From the Home screen, tap Camera 
 (in the QuickTap
Bar).
OR
With the backlight off, press either of the Volume
Keys 
 for a few seconds.
If you’ve set your phone to use the Swipe unlock
method, from the locked screen, simply press the Power/Lock
Key 
, or the Home Key 
, then drag the Camera icon 
 upward to open the Camera app.