Steadicam refers to a professional camera mounting system that combines the steadiness of dolly-mounted camera shots with the mobility of camera sliders. Traditionally, a handheld camera could only be used in documentaries or in limited fashion to create a heightened dramatic realism in fictional films–the instability of a hand-held camera is simply undesirable on a large screen for prolonged periods of time. A dolly-mounted camera, on the other hand, can provide smooth tracking shots, but requires much more planning, labor and space, and is limited to the tracks laid or prepared surfaces. A steadicam mount solves these obstacles by letting an operator isolate a handheld camera from his own movements, producing smooth, dolly-like shots. The purpose of the Steadicam, then, is not to produce anchored stationary shots, but to eliminate unwanted tilt, pan or roll in moving shots. One of the most important features of the steadicam is its isometric arm, which separates the camera from the operator. The camera arm, like a human arm, has upper arm and forearm segments separated by a joint. Inside each segment is a complex system of pulleys and springs connected to a cable. If the springs were used alone, they would expand and contract according to the force exerted upon them, not providing much benefit. The compound pulley system is used to counteract the movement in the spring. The result is that the spring absorbs external forces and the pulley minimizes its impact on the cable and to the camera. The isometric arm is connected to a vest worn by the operator, whose relatively small movements no longer jostle the camera, but who can still manipulate its angle and direction. On the other end of the isometric arm is the actual camera mount, called the sled. It is the other essential feature that creates the benefits of the camera slider dolly. By placing the camera on the opposite end of the sled as the battery pack and LCD monitor, it takes the center of gravity of the rig out of the camera itself, making it less likely to be jostled by small movements. Even more importantly, the center of gravity is moved to a point near a central gimbal in the sled. A gimbal is commonly used to keep objects steady. For example, in navigation, it can keep a compass parallel to the horizon despite a plane or ship’s pitching and rolling. The spread of the overall mass, and the use of a central gimbal, combat the unwanted tilt, pan and roll of conventional handheld camera work while allowing the operator to move the camera as desired, producing a relatively steady picture even if the operator is running.