In the upcoming insider preview Windows 10 Mobile builds a new feature is spotted where the lock screen seems to have a camera button which will give users fast and direct access to the Camera. It has been a most requested feature that Insiders have been looking for since Windows Phone 8.1 launch back in 2013.
Camera can be accessed by holding the camera button on the navigation bar on lock screen. Phone will vibrate just like doing it with a dedicated camera buttons when pressing the button. Users with a device that has a dedicated Camera button will probably be able to have option to remove it. Untill it is available, users can use the camera toggle on action center to launch camera on lock screen.