HOW IT WORKS; Making a Still Point in a Turning World
WHEN Michael Hartog, a special effects director for television commercials, began work on a credit card ad recently, he did not just use a 35-millimeter movie camera, nor did he turn to one of the sophisticated new high-definition digital video cameras.
Instead, Mr. Hartog's camera of choice was the Canon EOS Rebel-G, a humble 35-millimeter still camera. Actually, Mr. Hartog took 88 of the cameras with him 9,000 feet up a mountain near Ogden, Utah, along with a battery of electronic equipment.
Mr. Hartog, who is president of Director's Cut, a visual effects company based in Los Angeles, was taking advantage of a sophisticated computerized system that allows him to create moving images by assembling sequences of still photographs taken in an array. "In my business you always look for something new," Mr. Hartog said.
The idea of capturing movement with photos taken by a series of still cameras is older than motion pictures. In 1877, Eadweard Muybridge, an English and American photographer, had a running horse trigger a series of camera trip wires to capture its motion.
Today, camera arrays are used for two broad purposes: to freeze part of the action as the camera appears to continue to move and to simulate movements that would be extremely difficult, if not impossible, for a conventional movie camera to make. The technique has been popularized in films like "The Matrix" -- in which jumping characters appear to freeze in midair while action continues around them -- and it has found its way into television commercials and music videos.
Mr. Hartog, in his commercial promoting Visa's sponsorship of the Winter Olympics in Salt Lake City, wanted to create a slow-motion image of a snowboarder who appears to have jumped off a rock ledge. But a rapid, 180-degree rotation of the camera reveals that the snowboarder actually leaped from a helicopter (the actual leap was only 24 feet, into a soft bag).
The system that Mr. Hartog used, known as the Multicam system, was developed by Reel EFX, based in North Hollywood, Calif. Jim Gill, the vice president and co-owner of Reel EFX, said he was approached in 1996 by the producers of a commercial for Nike featuring the tennis star Andre Agassi. To emphasize the power in Mr. Agassi's serve, the makers of the commercial wanted to follow alongside a tennis ball that had been smashed by Mr. Agassi's racket.
Because Mr. Agassi's serve travels at more than 100 miles an hour, Mr. Gill determined that even if he could make a camera travel that fast, it would be damaged by the acceleration.
Recalling the Muybridge photos, Mr. Gill decided that one way to follow the ball might be to calculate its movement in advance and then position still cameras along a rail to simulate tracking by a movie camera. Fortunately, Canon was also one of Mr. Agassi's sponsors, and the company agreed to provide 100 cameras and lenses for the experiment. The cameras were mounted on a rail and after some complicated calculations, were fired in sequence by software run by a laptop computer.
To convert a series of still photos into movies, Multicam users gather exposed film, splice it for processing (to avoid color and exposure variations) and scan the resulting negative into a computer.
Because the frames on the film of a still camera are roughly twice the size of motion picture frames, technicians have plenty of space to adjust for differences in alignment among the cameras. The software assembles the still images and stores them on a DVD or digital tape. If the final product is to be projected, as a theatrical movie, for example, special printers can write the digital image onto film.
In Mr. Hartog's commercial, the effect of rotating, or dollying, the camera would have been impossible using a motion picture camera alone. Instead, technicians installed an array of 88 still cameras on an arc-shaped rail. The cameras were aimed and their firing sequence timed so the final commercial will have a seamless transition between the still-camera sequence and moving images of the leap before and after the 180-degree turn, shot by two movie cameras.
Or so Mr. Hartog hopes. The commercial is still in production.
Frozen action scenes are more straightforward. For a recent European vehicle advertisement, for example, Mr. Gill's company assembled a bank of cameras on a J-shaped rail that initially tracked the movement of the vehicle just as they had tracked Mr. Agassi's tennis ball, by firing sequentially. When the vehicle hit a bump that sent it flying into the air, the cameras -- including those on the curved part of the rail in front of the vehicle -- fired simultaneously. When played back in sequence, those simultaneous shots created the illusion that the vehicle had been frozen in midbounce in the sky as a camera continued to move around it.
Other camera array systems rely more on computers to avoid the complications of using 150 still cameras or more. (Reel EFX had to scour camera stores recently to find 140 lenses demanded by the special effects director of an upcoming feature film.)
BUF Compagnie, the company that worked on sequences for the film "Fight Club" and a 1998 commercial for the Gap, uses far fewer cameras -- seven -- to create movement through a 180-degree arc. The company, which is based in Paris, then uses morphing software to generate additional frames.
Many creators of special effects, including Mr. Hartog, regard frozen action created with still camera arrays as film's newest cliché. But Mr. Gill, who studied chemical engineering and philosophy before discovering the special effects business, contends that his system still has lots of potential.
Sequences that begin in water and end on land, for example, often present a problem for filmmakers. But Mr. Gill said he had recently used his system to shoot just such a sequence with ease. "There are a lot of things people haven't tried yet," he said.