A versatile motion-control system for photographing miniatures consists of a steady pin-registered camera, built into a pan-tilt-roll head wherein the entrance pupil of the lens can be situated at the vertex of all axes, hung from a boom arm, all mounted on a track of at least 50 feet in length. Various model movers, rotators, or pylons are usually mounted on another track of 20 feet or so set perpendicular to the camera track. Again, there are many variations on this basic theme incorporating various levels of engineering prowess within the industry and the precision and reliability of such systems provide the operators with different levels of creative freedom.
An electronic system runs the motors (usually stepping motors unless considerable speed or power is needed, in which case DC closed-loop servo motors are used), then stores the motion files laid down by the operator and enables the operator to interact with the system. There are many bells and whistles which include move-smoothing programs, graphics tablets, and specialized software ad infinitum.
Studio motion-control equipment often has provisions to control the camera shutter angle over a wide range in order to control the apparent motion blur. The exposure range is from about 14 second to extremely long. Most systems have several ways to program moves and any or all of the following methods may be used.
Joysticks (usually potentiometers or rotary optical shaft encoders) are used to manually move the motors that operate the various parts of the system. The joystick might control the speed or position of one or more motors at a time and all these motions are recorded for future playback. This is similar to remote controlling a model airplane or car and making an exact record of what happened.
The joystick might be used to move the system to a series of fixed positions while a record is made of these key positions. The system could later generate a mathematically smooth path through these points. This is similar to an animator drawing key frames and then creating all the in-betweens automatically.
If the system has a computer keyboard, then a move could be created using only start and end positions with ease-ins and ease-outs much like an animator's exposure sheet. Much more complex methods of move generation are available using computer graphics. The move files can be edited and modified in as many ways as there are mo-tion-control systems. Some computer-control systems have graphics which allow the operator to preview the shot before the camera is used.
A number of commercial electronic motion-control systems are available, as well as mechanical systems. Some of the major visual effects studios build their own motion-control systems. Although the use of motion control in modern effects work is commonplace, the process can be expensive and time-consuming, but when properly approached, high-quality visual effects can be produced at budget and on time.
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