American Cinematographer - May 2010 - 74

Tricks of the Trade
I
Creating a Virtual New York for 24 By Douglas Bankston Season eight of the series 24 features a United Nations peacekeeping crisis and a nuclear terrorism threat hanging over New York City. The show isn’t shot in New York, nor has the production traveled across the continent to film typical establishing shots, but that is the real U.N. headquarters visible in the background behind the CounterTerrorism Unit’s office. Thanks to Stargate Studios’ digital chicanery, 24’s director of photography, Rodney Charters, ASC, CSC, is able to exploit virtual New York sets without ever leaving L.A. “This idea of texture-wrapping reality into a virtual space and then reshooting it, motion-tracking it and slaving it to real camera movement is what we’re into,” says Stargate founder Sam Nicholson, ASC. Virtual sets are not new, but the most photo-realistic ones are usually seen in big-budget projects courtesy of VistaVision or high-end datacine cameras. That idea was turned on its head with the introduction of Canon’s EOS 5D Mark II digital SLR, which is capable of high-definition-video recording. The camera has an 18-megapixel sensor and costs $3,000-$4,000 fully outfitted. “A standard HD sensor is down in the 6-, 8- or 12-megapixel range,” says Nicholson. Still-photo plate elements as well as high-definition moving elements are shot in High Dynamic Range, which enables Nicholson’s team to “access a lot of color depth and range,” he says. “A standard HD frame is about 6MB uncompressed in DPX, whereas any one of our Virtual Backlot frames is running at 100-200MB. They are massive, but I can zoom in 800 percent and the resolution holds up.” If you composite a foreground element into a 2-D HDR background, the resulting image will look flat and fake, and 24’s handheld shooting style complicates matters. “The plates have to be what we call ‘dimensionalized’ — texture-mapped onto three-dimensional surfaces,” explains Nicholson. “When you move handheld on your foreground subject, your background retains all the proper parallax so that it doesn’t appear to be flat. The midground is really what this is about: The further out you go toward infinity, the flatter things become, so the background can be flat while the midground is dimensionalized and the foreground is live action. We can do that to such an extent now that we can walk entire city blocks in a photo-real virtual environment.” For example, the CTU helicopter pad is supposed to be on a grassy knoll on Roosevelt Island, with the U.N. complex across the water in the background. In actuality, the helicopter and the actors are shot in Rye Canyon in Valencia, Calif. Charters explains, “We shoot our actors running across a grassy knoll in Valencia with an extreme long lens, and we push a 20-by-20 greenscreen on wheels behind them. We’re cowboy-framing them, and as long as we keep them on the greenscreen, it sells. As the helicopter pulls away, we want to follow it; Stargate segues from traffic across the shore and boats
74 May 2010

The New York skyline is added to a scene from 24 via background elements shot with the Canon EOS 5D Mark II digital SLR.

going by into the hi-res file, and we can chase the helicopter with extraordinary resolution. You look at the sequence and think the actors are in New York.” The Canon 5D shoots HD video in 1920x1080 24p in AVCHD compression, a much lower resolution than the HDR still frame, so Nicholson embeds only the elements in motion in the massive HDR background plate. Each completed frame can be a composite of 20 or more different types of images. “We combine multiple resolutions of motion pictures, still images, computer graphics and digital matte paintings into a single, very-high-resolution background plate,” explain Nicholson. “Our background environments are then digitally matched with the live-action foreground camera dynamics of each take.” Another helpful byproduct for cinematographers is the ability to freeze time. “We can shoot the perfect magic-hour backdrop for any scene,” says Nicholson, “and it will stay magic hour for as long as necessary because we’re on a set, lighting it for magic hour. “It is critical for the director of photography to be a part of that process on set,” he notes. “We can do a finished-quality highdefinition composite on set with two cameras handheld, and the cinematographer can see how to light and frame the greenscreen sequence. If the sun is dipping in and out of trees, he can see that in real time and tune the reactive lighting accordingly. Rodney’s involvement at this level is why we get the realistic look we get on 24.”●

American Cinematographer

Images courtesy of Stargate Studios.

American Cinematographer - May 2010

Table of Contents for the Digital Edition of American Cinematographer - May 2010