James Cameron's 3-D epic Avatar wowed audiences with its immersive special effects, but Hollywood is hoping the technology can do something more: Give film studios breathing room in the fight against movie piracy.

"There is going to be a good period where 3-D has got a little more value, because it can't be purloined from the theater," said Michael Peyser, a University of Southern California (USC) professor of production and executive producer of 2007's U2 3D.

"There's no commodity to it, nor can the files, even if they're copied, be viewed."

Indeed, the market for knockoff films in 3-D is currently nonexistent, because almost no one has the means to watch them at home. But that could change soon: Sony, Panasonic and Samsung all plan to release 3-D-compatible TVs in 2010. If 3-D goes mainstream, the demand for pirated 3-D movies will grow. The question is, will pirates be able to reproduce the movies' 3-D effects, or will they be stuck shilling 2-D versions of 3-D blockbusters?

Pirates usually make illegal copies of films in one of two ways, according to the Motion Picture Association of America. Either they sneak a camcorder into a theater, or they break the security codes on legitimate or pre-release screener DVDs and make copies at will. The pirated movies are then made into illegal DVDs or distributed on file sharing sites as downloadable "torrents".

The camcorder trick is responsible for up to 90 percent of pirated new releases. The low-quality 2-D copy of Avatar circulating online is one of these so-called "cam" copies, said Ernesto Van Der Sar, founder of the torrent-tracking Web site TorrentFreak.

But camcorders aren't much use for pirating in 3-D, said Rick Heineman, a spokesman for 3-D technology company RealD. The images on a 3-D film are made up of two projections of differently polarized light. Polarization lines up light waves so that they all vibrate at the same angle.

The 3-D glasses worn by viewers filter one strain of polarized light to each eye. Because the two projections are slightly offset, each eye gets a slightly different image, creating the illusion of depth. In the case of RealD, which provided the technology for Avatar, the screen flickers back and forth between each polarization at 144 frames per second, six times faster than a typical movie.

"If you record a 3-D image with a handheld [camcorder], then you're just going to end up with a blurry image," Heineman said.

The story is murkier when it comes to ripping off 3-D Blu-ray discs, mostly because the technology is so new. Copying a 3-D film will likely be more difficult than copying in 2-D, USC's Peyser said, but it won't be impossible. Studios may be able to add extra security to such discs to prevent both polarized images from being copied at once. Still, such measures are unlikely to deter piracy for long.

"Pirates are pirates," Peyser said. "They will figure out a way of copying it."