HARRY POTTER
 • page 2
 • page 3
DVD
 • page 2
 • page 3

The final part of the Time-Turner sequence combines three elements: the clocktower exterior, the children running below and the surrounding environment. When preparing to light the miniature, Stone was in close touch with Burke, who was in Scotland, where the castle surroundings were being shot. He told Stone the precise angle of late-afternoon sunlight that would hit the castle bridge, and Stone lit his model to match. He made his first pass on a 1/24-scale model using stills from three camera positions, then went back and shot the same view on the 1/10-scale courtyard, which replaces the inner core of the 1/24-scale model. "I survey every lighting setup we do," says Stone, "so we've got the compass bearing on every lamp, the angle of tilt, the height and so on. I can extrapolate those figures onto anything else we shoot so we can match to ourselves pretty accurately."

This lighting data was then passed to the second unit at Leavesden, who filmed the running figures in the courtyard. "We needed to be as high as possible, so those images were shot on the runway from a Strada crane that was about 120 feet in the air," says Burke.

All of this work went into a sequence that will last for two minutes on the screen. "Alfonso said, 'People will remember those shots,'" says Guyett, "and I hope they do. They involve CG environments, animated creatures, the model, Steadicam, sets and bluescreen. It's incredible how much effort went into it, and it really pays off."

On a production as complex as The Prisoner of Azkaban, storyboards are critical to keeping legions of workers on track. So were the 35mm dailies for Seresin, who viewed them every morning to sign off on second-unit and model work and to check his own. "On a film of this scale, it's too dangerous to watch dailies on video," he maintains. "If something had been okayed on digital dailies and a problem arose down the line, the ramifications could have been massive."

Another essential tool was a comprehensive lighting log. "On this film," says Seresin, "we had one person, sometimes two, whose sole job was writing down every light and what it was doing. There's a plan, probably 500 pages of the most incredible drawings, of every setup, every light, every piece of diffusion, where it was on a dimmer, when a lighting change was done on a scene. It's almost a master class in exposure, lens and focus." The log was also a blueprint for the widely scattered photography units and CG animators.

As valuable as these tools were, there was nothing like face-to-face dialogue. From prep through post, Seresin and the effects supervisors were closely involved in each other's work. "The Patronus is a good example of time well spent with Michael during prep," says Guyett. The Patronus is a protective force field that springs from a wizard's wand and resembles a traveling 3-D balloon of light - a relatively simple effect in the scheme of Harry Potter. "We asked ourselves what that means practically," says Guyett. "What does it do to the room, and how you work with that? The more you can establish in-camera, the better the effect is going to be."

When the Patronus had to sweep across a lake during a climatic scene shot at Leavesden, Seresin's lighting - a series of Mini-Brutes on dimmers - set the pace for the 3-D Patronus and provided the interactive element. "We had phenomenally powerful sources in a scene that was otherwise set up to be very low-key, which just burned things out," Seresin recalls. "We used [the Mini-Brutes] at different levels so the team at ILM would have different densities to work with. The burnout was probably 10 stops brighter than anything else."

Of all the CG characters, the Dementors proved the most difficult to conceptualize. Seresin filmed tests of various maquettes underwater, allowing the designers to see how the creatures' tattered fabrics might float in a supernatural way. "We tested with different fabrics and different lights - frontlight, backlight, crosslight, overcranking, undercranking, normal speed - to arrive at a movement and a feeling for it," says the cinematographer. Cuaron then looked at the rushes and picked out specific movements, which were passed on to ILM as reference points along with fabric samples, maquettes, drawings and, eventually, the lighting log. "Ultimately," says Guyett, "we wanted to light our creatures as though they were real and Michael Seresin was lighting them."

During production, the CG characters had various stand-ins that provided eyelines and facilitated shot composition. For the Dementor, a model on a stick often did the trick. For the hippogriff, a real horse or animatronic served the purpose. But when Harry flew the hippogriff, a rough composite was made while shooting bluescreen. The background elements had already been created - the aerial footage in Scotland, and the hippogriff in a computer. On the bluescreen stage, Radcliffe was strapped to a motion-control rig that was programmed to replicate the hippogriff's movements. "Using After Effects, we composited the video-tap performance of Daniel riding the motion base from the bluescreen onto the pre-rendered CG hippogriff and the backgrounds from Scotland," says Burke. "After Effects had a predetermined CG camera move that worked in conjunction with the motion-control move to seat Harry on the back of the hippogriff correctly. This strategy allowed Alfonso to see almost real-time composites of Daniel's performance on set."

This departmental duet continued well into postproduction. At press time, Seresin was wrapping up two months of CG viewing. (Altogether, he devoted four months to postproduction). Every morning he spent about five hours approving effects shots before handing them over to colorist Peter Doyle (The Lord of the Rings) at Warner's DI facility. "We're not changing animation, we're just adding shadows or highlights," he says. "Then I look at the filmout of a sequence or series of shots at Technicolor in London. I rarely bother looking at it on tape - to be dead blunt, what it looks like when it's filmed out is what counts. It's also vital to look at the filmed-out reels on large cinema screens, because that's where quality issues are paramount."

Seresin's lighting expertise helped troubleshoot problems on the CG renderings, such as a particularly bothersome shot of Harry riding the hippogriff. "He's sailing along, and as we tracked into his face it just seemed phony," says the cinematographer. "None of us could figure out why." After a few weeks, "we discovered that we needed to enhance the CG light from the sky and flare it out a bit, and, as the camera started to track, we needed to throw [the hippogriff's] head slightly out of focus." After a final touch of CG atmospheric haze was added, Seresin says, the shot "was finally integrated into the rest of the sequence." Adds Guyett, "When CG lighting doesn't quite match the world, you have to start exploring why. We sat down with Michael and Alfonso and discussed the strength of the key light, the strength of the fill, the amount of backlight and all of those kinds of considerations. Then we worked with the companies doing the lighting and compositing to bring those elements into line."

"Michael is an extremely knowledgeable cameraman and a smart guy as well," says Burke. "He plays down his technical side, but he and Alfonso picked up very quickly on how to go about this kind of work."