To open the Camera app
From the Home screen, tap Camera
(in the QuickTap bar).OR
With the backlight off, press and hold the Volume Down Key
(on the back of the phone).
TIP!
If you’ve set your phone to use the Swipe unlock
method, from the locked screen, simply press the Power/Lock
Key 
(on the back of the phone), then drag the Camera icon upward to open
the Camera app.