With Episode II, the DMR process was spared a step in that the image content already existed in a digital state; there would be no film to scan. But starting from an HD-source brought its own technical issues, as the algorithms set in place for handling a 35mm source wouldn't entirely suffice for the re-mastering of Clones
"In a digital film, it doesn't obviously have grain that we've come to know in normal photography," explains Bonnick. "But it does tend to carry 'video noise' artifacts. Two noticeable ones would be when pixels appear to be off-color relative to those in the surrounding area. You might get a flicker from frame to frame. Or when tighter clusters of pixels tend to slightly vary in color from frame to frame. That tends to happen in dark areas, and it looks a bit like a boiling effect. Now these are very, very subtle effects; in most cases I'd have to take you into a theater and describe to you what to look for and you would find it. Somebody who is very up on video would really pick these sort of things up; obviously, in our industry that's part of our job."
The DMR pipeline was customized to deal with these unique forms of artifacts. "We've designed it to be very open-ended. If we come across an artifact that we've never dealt with before, we're in a position to very quickly write a new algorithm and incorporate it into the production engine in a short period of time."
Though the software examined each and every frame of image, the re-mastering team broke the film down into shots as discreet units of work and focus. An individual shot (a sustained hold from a camera vantage point prior to it cutting to the next "shot") is fairly uniform in its re-mastering requirements, though if there are specific artifact issues within a shot, the team then redirects their efforts to the more focused scale: individual frames.
The image re-mastering process took about 14 weeks of work, and was finished by the end of September 2002. "The process is scalable," says Bonnick. "At the moment, we've got dozens and dozens of computers in our render farm. It's all a factor of how many frames per day you want to process. If you want to process more frames per day in a given timeline under a tighter deadline, then you would scale up the numbers of computers in your system to give you greater throughput capacity."
The IMAX Experience™ is more than just big picture. It also delivers six-channel uncompressed multi-speaker sound that further completes the audience's total immersion into Episode II. "We use six completely discreet channels plus subwoofers on their own separate channels. We use ultra-low distortion amplifiers, capable of delivering up to 12,000 watts of power. We employ our own custom-designed speaker-set with over 44 speakers," explains Bonnick. That sound system is carefully aligned by lasers to deliver proportional point source (PPS) quality.
"The non-technical definition of a PPS speaker is that we have designed it such that, rather than having the dead-center seat in the theater being the 'sweet spot,' these speakers are designed to enlarge the sweet spot quite a bit so that everybody in the theater is sitting in a good position to hear the sound as it was originally intended," explains Bonnick.
The IMAX sound system will not only deliver huge events like the shattering of asteroids or the crash of a core ship, but also soft sounds like the distant birds of Naboo or the hum of background cloning machinery with crystal clarity. "The IMAX sound system has been designed with a very high dynamic range, unlike 35mm theaters. There, when you start to get anything with depth or volume to it, you tend to hear a lot of distortion."
Those fortunate enough to have caught the original digital exhibition of Episode II in the spring are probably digital-converts, fully aware of the limitations of traditional film. IMAX film is a whole different set of variables, since the quality-assurance and technical advancements in projecting films of this size help overcome many of the limitations of 35mm exhibition.
"IMAX film lasts substantially longer than 35 mm film, because we use the rolling loop technology in our projectors," explains Bonnick "The film is moved around the lens aperture in a wave motion. We're not moving it constantly through sprockets that over time wear the film out and enlarge the perforations, which is when you start getting a jiggle in the film. Because of this fluid motion that the IMAX film goes through, we are being very gentle to it, ergo it lasts longer."
An IMAX projector has a steadiness of .004 percentage change from frame-to-frame. A traditional 35mm film has a .12 steadiness in comparison. Even the heat of the projection bulb will cause a 35mm film to buckle, something that can't happen in an IMAX projector thanks to a field flattener that holds the film steady and true.
Furthermore, the smaller number of IMAX screens makes quality assurance easier to manage. "The systems are constantly being tuned to ensure the films are running properly, that the steadiness is accurate, and the light intensity and distribution of it are all set adequately, that the screens are clean, that everything is at optimum performance levels."
An IMAX projector is an immense machine, weighing in at over two tons. The huge platter that spins the oversized film has an upper limit of film length. Most films that play in IMAX theaters are documentaries that don't clock in much over an hour in length. Feature films have to be cut to 120 minutes since that is the current maximum the platter can sustain. For number-minded trivia fans, the Episode II IMAX print is 58 inches in diameter and weighs 390 pounds! "It's the limit now," explains Bonnick. "We are actively developing a 150-minute solution that would be employed as an upgrade to the theaters in the future."