If the iPhone is locked, there’s a shortcut to quickly open the Camera app. Swipe from right to left across the Lock Screen until the Camera app appears. Bear in mind you can’t return to the lock screen by swiping back the other way – you’ll need to press the Home button instead.
For security, if the Camera app is opened in this way, only the photos just taken can be seen; other items in the Camera Roll won’t be accessible.
