To open the Camera app

Tap the Home button
> Camera
.

From any Lock screen except Swipe, drag the Camera icon
at the lower-right corner to the left.

TIP

With the backlight off, press the Volume Down button twice to immediately take a quick picture using the Auto camera type and the last lens selected. Enable the Quick shot switch in the Shortcut key settings to enable this shortcut feature (disable the switch for the shortcut to just activate the Camera app with the Volume Down button).