Virtual back lot from Stargate Studios brings the world to L.A.

A stone-faced Kiefer Sutherland, star of the Fox TV show “24,� grabs the throttle of a mock helicopter propped up on a soundstage that has been wheeled in front of a giant blue screen.

The actor is performing on a stage inside a converted warehouse in Chatsworth, but the on-screen action -- a low-altitude aerial scene in which Sutherland’s character, the intrepid Jack Bauer, is being chased by two Air Force helicopters -- is meant to take place over midtown Manhattan.

But the producers didn’t have to fly to New York to capture the scene for an upcoming episode of “24,� a costly, not to mention problematic, task given heightened security concerns about low-flying aircraft in New York. Instead, helicopter landing and take-off scenes were filmed in Valencia and downtown L.A., and producers used aerial footage of New York from a “virtual back lot library� compiled by Stargate Studios, a visual effects production firm in South Pasadena.

Brad Turner, director and executive producer of “24,� says the availability of such technology was one of the key reasons the show has remained in Los Angeles despite the incentives luring film production out of state.

“It’s a huge factor,� Turner said. “Every day we get more and more roadblocks about what we can and can’t do.� But with the new technology, he noted, “I can create any environment I want.�

At a time when Southern California is struggling to hold on to its movie and TV production industry, Stargate Studios has developed an advanced green screen technology that allows filmmakers to feature scenes from around the world without leaving L.A.

The green screen technology -- a film technique in which actors perform in front of a blank screen, typically green or blue, that is later replaced by an alternate background -- has been available for years, but mostly for feature films. The advent of low-cost digital cameras and more high-powered computers, however, has opened up the process to TV producers as well, creating opportunities for firms such as Stargate.

Stargate, one of several studios specializing in green screens, provides virtual environments for a growing number of locally produced TV shows, including “24,� NBC’s “Heroes� (set in New York and other locales), ABC’s “Grey’s Anatomy� (Seattle) and TNT’s “Saving Grace� (Oklahoma City).

“It’s like bringing remote locations to L.A. rather than� traveling to them, said Stargate Chief Executive Sam Nicholson. “If you can bring the Vatican to L.A., then why go to the Vatican?�

Such questions inspired Nicholson, a visual effects supervisor and cinematographer, to launch Stargate in 1989,when digital technology was in its infancy. Today, Stargate generates $15 million in annual revenue and employs 150 digital artists, producers and technicians. The company has studio outposts in Toronto and Vancouver, Canada, but most of its work is handled out of Los Angeles.

When he’s not on film sets, Nicholson travels the globe, using lightweight digital cameras to capture footage of landmarks in cities such as Paris, New York, Tokyo and Rome. He has collected more than 1,000 hours of video consisting of 100,000 high-definition clips from 50 cities. This week he will go to Mumbai, India, to film a giant call center for an NBC pilot titled “Outsourced.�

Shooting the video is just the first step. Next, Nicholson and his team must “stitch� together the various video clips to compose a panoramic picture. Visual effects artists then design a three-dimensional computer model of the video, which can be digitally manipulated to portray, say, a wide-angle street view.

Actors are afterward inserted or “nested� into the virtual world, by performing in front of high-resolution cameras and a giant green screen (although some are blue). Directors can see the finished product as they shoot, making the necessary adjustments to lighting and camera position -- just like on a regular film set.

“The camera becomes like a magic box you can see in,� Nicholson said.

Of course, technology alone is not a solution for runaway production. Stargate itself learned that two years ago when production of a show it worked on, the ABC sitcom “Ugly Betty,� relocated to New York from Los Angeles to take advantage of film tax credits offered there. The move prodded California to enact film tax credits last year.

Nonetheless, producers of some major network TV shows credit Stargate’s technology for helping to keep their shows in town.

“Everybody wants to sleep in their own bed, but the economy is making that more and more difficult,� said Dennis Hammer, executive producer of the sci-fi drama “Heroes,� now in its fourth season. “This is a technology that, if it’s used properly, can certainly make a stronger case for production staying in L.A.�

richard.verrier@

latimes.com