Apple added a number of new features to the camera in iOS 5, as more and more users drop their point-and-shoot digital cameras in favor of the increasingly powerful cameras built-in to smartphones.
For users looking to take pictures quickly, when the phone is locked, simply press the home button twice -- then press the camera icon that appears to be taken directly to the camera. This works even when the phone is locked with a passcode.
Apple's engineers also added a feature that caused Camera+, a popular camera app, to be banned from the App Store for four months. Users of Apple's standard camera application can press the volume-up button to take a snapshot, rather than pressing the shutter button on the touchscreen. This makes the iPhone more like a standard camera, with the shutter release on the top.
Article Link: iOS 5 Camera: Volume Shutter, Lock Screen, Remote Triggering