Motion control photography
Encyclopedia
Motion control photography is a technique used in still and motion
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...

 photography
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...

 that enables precise control of, and optionally also allows repetition of, camera movements. It can be used to facilitate special effects photography. The process can involve filming several elements using the same camera motion, and then compositing
Compositing
Compositing is the combining of visual elements from separate sources into single images, often to create the illusion that all those elements are parts of the same scene. Live-action shooting for compositing is variously called "chroma key", "blue screen", "green screen" and other names. Today,...

 the elements into a single image. Other effects are often used along with motion control, such as chroma key
Chroma key
Chroma key compositing is a technique for compositing two images together. A color range in the top layer is made transparent, revealing another image behind. The chroma keying technique is commonly used in video production and post-production...

 to aid the compositing. Motion control camera rigs are also used in still photography with or without compositing; for example in long exposures of moving vehicles. Today's computer technology allows the programmed camera movement to be processed, such as having the move scaled up or down for different sized elements. Common applications of this process include shooting with miniatures, either to composite several miniatures or to composite miniatures with full-scale elements.

The process is also commonly used when duplication of an element which cannot be physically duplicated is required; motion control is the primary method of featuring multiple instances of the same actor in a shot that involves camera movement. For this technique, the camera typically films exactly the same motion in exactly the same location while the actor performs different parts. A blank take (with no actor in the shot) is sometimes also taken to give compositors a reference of what parts of the shot is different in each take. This, in common film-making language is also known as shooting a "plate".

In today's film, the reference take is also useful for digital manipulation of the shots, or for adding digital elements. A simple duplication shot confines each "copy" of an element to one part of the screen. It is far more difficult to composite the shots when the duplicate elements cross paths, though digital technology has made this easier to achieve. Several basic camera tricks are sometimes utilized with this technique, such as having the hand of a body double enter a shot to interact with the actor while the duplicate's arm is to be off-screen. For the sake of compositing, the background elements of the scene must remain identical between takes, requiring anything movable to be locked down; the blank reference take can aid in resolving any discrepancies between the other shots.

Similar technology in modern film allows for a camera to record its exact motion during a shot so that the motion can be duplicated by a computer in the creation of computer generated elements
Computer-generated imagery
Computer-generated imagery is the application of the field of computer graphics or, more specifically, 3D computer graphics to special effects in art, video games, films, television programs, commercials, simulators and simulation generally, and printed media...

 for the same shot.

History

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
Catch-22 (logic)
A Catch-22, coined by Joseph Heller in his novel Catch-22, is a logical paradox arising from a situation in which an individual needs something that can only be acquired with an action that will lead him to that very situation he is already in; therefore, the acquisition of this thing becomes...

: 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
Depth of field
In optics, particularly as it relates to film and photography, depth of field is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image...

, 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
John Whitney (animator)
John Whitney, Sr. was an American animator, composer and inventor, widely considered to be one of the fathers of computer animation.-Life:...

 pioneered several motion techniques using old anti-aircraft analog computer
Analog computer
An analog computer is a form of computer that uses the continuously-changeable aspects of physical phenomena such as electrical, mechanical, or hydraulic quantities to model the problem being solved...

s (Kerrison Predictor
Kerrison Predictor
The Kerrison Predictor was one of the first fully automated anti-aircraft fire-control systems. The predictor could aim a gun at an aircraft based on simple inputs like the observed speed and the angle to the target...

) connected to servo
Servomechanism
thumb|right|200px|Industrial servomotorThe grey/green cylinder is the [[Brush |brush-type]] [[DC motor]]. The black section at the bottom contains the [[Epicyclic gearing|planetary]] [[Reduction drive|reduction gear]], and the black object on top of the motor is the optical [[rotary encoder]] for...

s to control the motion of lights and lit targets. The 1968 film 2001: A Space Odyssey
2001: A Space Odyssey (film)
2001: A Space Odyssey is a 1968 epic science fiction film produced and directed by Stanley Kubrick, and co-written by Kubrick and Arthur C. Clarke, partially inspired by Clarke's short story The Sentinel...

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 first large-scale application of motion control was in Star Wars Episode IV: A New Hope
Star Wars Episode IV: A New Hope
Star Wars Episode IV: A New Hope, originally released as Star Wars, is a 1977 American epic space opera film, written and directed by George Lucas. It is the first of six films released in the Star Wars saga: two subsequent films complete the original trilogy, while a prequel trilogy completes the...

(1977), where a digitally controlled camera known as the Dykstraflex
Dykstraflex
The Dykstraflex is a motion picture camera system named after its primary developer John Dykstra. Numerous people actually created the camera, with the critical electronics being created by Alvah J. Miller and Jerry Jeffress. The camera was developed specifically for complex special effects shots...

 performed complex and repeatable motions around stationary spaceship models. This enabled a greater complexity in the spaceship-battle sequences, as separately filmed elements (spaceships, backgrounds, etc.) could be better coordinated with one another with greatly reduced error.

In the UK The Moving Picture Company had the first practical motion control rig. Designed and built in-house, it used the IMC operating system to control its various axis of movement. Peter Truckel operated it for several years before leaving to pursue a career as a successful commercials director.

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
Match moving
In cinematography, match moving is a visual-effects, cinematic techniques that allows the insertion of computer graphics into live-action footage with correct position, scale, orientation, and motion relative to the photographed objects in the shot...

), initially made the use of motion control photography less common. However film producers and directors have come to realise the cost-saving benefit of using motion control to achieve the effects in a reliable and realistic way. CGI still struggles to be 100% photorealistic, and the time and cost to achieve photo-realistic shots far exceeds the cost of shooting the live action itself.

With the resurgence of 3D as a medium motion control has also an important role to play, especially in the production of 3D background plates on scaled-sets. Using high resolution still cameras, backgrounds can be easily shot for further use with live action and CGI character animation.
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