Motion control photography
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Motion control photography is a special effects technique used in film that enables precise repetition of camera movement, usually to facilitate special effects photography. Its first large-scale application was in Star Wars Episode IV: A New Hope, where a digitally-controlled camera known as the Dykstraflex could perform complex and repeatable motions around stationary spaceship models. This enabled a greater complexity in the spaceship-battle sequences, in that separate effects elements (spaceships, backgrounds, etc.) could be better coordinated with one another, and that such elements could be created and duplicated precisely and with greatly reduced error.
Modelmaking for scenery has long been used in the film industry, but when a model is too small it often loses its illusion and becomes "obviously a model". Solving this by building a larger model introduces a catch-22: larger models are more difficult to build and often too fragile to move smoothly. The solution is to move the camera, rather than the model, and the advent of compact lightweight 35mm cameras has made machine-controlled motion control feasible. Motion-control also requires control over other photographic elements, such as frame rates, focus, and shutter speeds. By changing the frame rates and the depth of field, models can seem to be much larger than they actually are, and the speed of the camera motion can be increased or decreased accordingly.
Early attempts at motion control came about when John Whitney pioneered several motion techniques using old anti-aircraft analog computers (Kerrison Predictor) connected to servos to control the motion of lights and lit targets. The 1968 film 2001: A Space Odyssey pioneered motion control in two respects. The film's model photography was conducted with large mechanical rigs that enabled precise and repeatable camera and model motion. The film's finale was created with mechanically-controlled slit-scan photography, which required precise camera motion control during the exposure of single frames.
The simultaneous increase in power and affordability of computer-generated imagery in the 21st century, and the ability for CGI specialists to duplicate even hand-held camera motion (see Match moving), has made the use of motion control photography less common.
