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Assessing the Merits of 24-Frame Video Playback [American Cinematographer, The](American Cinematographer, The Via Acquire Media NewsEdge) Since the beginning of time, or at least since Howard the Duck (1 986), the first movie I ever worked on, TV monitors have been blue. While preparing to shoot a scene in the apartment occupied by the main character, Beverly (Lea Thompson), Richard H. Kline, ASC told me to "warm it up a little bit! " The sets were built in a brutally cold San Rafael warehouse, and most of us were gathered around portable gas heaters or bundled up in Arctic gear. Rubbing my hands together, I replied, "Yeah, it's realty cold." Richard gave me an odd look, then pointed to the TV and said, "It's too blue." I looked down at the TV and realized he was not commenting on the temperature onstage, but was instead referring to the color temperature of the TV. This was my first solo mission, and I had only been working for Video Image, a pioneer in the burgeoning field of 24-frame video, for a few months. I gave Richard a thumbs up, as if to say, "I knew that," and casually walked back to my playback machines. In those days, 24-frame playback material was mastered on W U-Matic cassettes containing two passes of the same material. The first pass was corrected for tungsten (3,2000K), and the second pass was normal, or daylight (4,5000K). I cued up the corrected pass and hustled back out to the set. The image on the TV was an unnerving shade of orange, but when I viewed it through my 8OB filter, it looked normal. I made a few adjustments to the TV, set the exposure and, using a sync box on the camera, rolled out the shutter. Richard checked h with his meter and gave me the nod. Of course, I wouldn't really know if I'd screwed up until dailies were screened the next day, so I was nervous. As it turned out, the monitor looked fine, and although I was feeling really impressed with myself, no one else seemed to even notice - they commented on how good the actors and set looked, how moody the lighting was or how sharp the focus was. That, of course, is the way it should be: unless the color or exposure is off, or if, God forbid, there's a shutter bar flickering aaoss the bottom of the screen, no one should notice the TV in the scene. Today, although we have flat-screen LCD monitors, plasma screens with fluorescent backlights, and DLP projectors with bright, shimmering mirrors, things haven't really changed much. The new flat screens are really cool, but that's the problem: they're really, really cooi. The old tube-type CRT televisions burned around 4,5000K, whereas the new flat screens burn anywhere from 6,000-1 4,0000K and are far greener than their predecessors. The first time! worked with a plasma screen was on Enemy of the State (1998). Everyone was excited about the new technology and darned it would all but eliminate the need for 24-frame video sync. Keen to promote the world's first flat-screen plasma TV in this high-profile film, Phillips sent over a few of its soon-to-be-released 42" plasma screens. During prep, the director of photography, Dan Mindel (future ASC), suggested we include the plasma in the camera tests. Using the standard correction tools of the time, a pre-recorded tape corrected for 3,2000K and an 8OB filter, I adjusted the color on the screen for tungsten light. No matter how much tweaking I did, however, the color just didn't look right I checked it with my Minolta color meter, and, sure enough, the temperature was decidedly green. This, of course, was the result of the fluorescent backlight. Using the tint controls on the Phillips monitor, I was able to add enough magenta so the image looked "normal" on the meter. But this new technology had one other artifact to reveal. Because plasma screens are not based on the scanning technology of CRT monitors, everyone assumed it would not be necessary to feed it with a 24-frame video source and sync it to the camera. This bit of misinformation revealed itself all too dearly when our film test was screened the following day: a rolling shutter bar could be seen floating down the plasma's massive screen. If anything, plasma technology has made the video engineer's job more challenging. It's still necessary to sync the screens to 24frame and color correct them. The real problem, however, is that most plasma screens won't accept the oddbali frequency generated by a 24-frame video system, and finding one that will is always frustrating. As a result, all the screens featured in Enemy of the State were old, reliable CRT monitors, including the video wall in NSA headquarters. LCD technology was available at the time - we had used such screens extensively a few years earlier on Demolition Man (1 993) - but plasma was the only technology available in a large-format screen. LCD technology seemed almost foolproof at first, requiring only a standard 30frame video signal. The only downside at the time was a very narrow sweet spot limiting your angle of view. In a Demolition Man scene that shows the prison warden (played by Mark Colson) talking to Huxley (Sandra Bullock) on a handheld device, it was necessary to attach the screen to the actor and the dolly with a C-stand arm to maintain its angle to the camera. As the technology advanced, the screens got better and larger, but some of them revealed other problems. The newer backlight units are increasingly susceptible to the flicker and flutter similar to that of an unregulated 50-cycle European light source. If you saw the latest Star Trek movie (AC June '09), which offered me another chance to collaborate with Dan Mindel, you might remember the seamless video screen that wrapped around the perimeter of the bridge of the Enterprise. This was built from a customized Orion display system using 1 6 42" plasma screens placed side by side. The rest of the set was populated with dozens of large LCD screens displaying the various control surfaces of the ship. A few days before filming was scheduled to begin, we prepared to shoot a camera test on the bridge. I balanced the color on all the monitors by displaying a gray-scale chart on each screen, then set the exposure and shot the test. The LCD screens looked great, but there was a major flicker rolling through the plasma screens, even though we were feeding them a 24-frame signal. This set was designed around the plasmas, and they couldn't be easily replaced. After Dan and I discussed all our options, he decided to use a 1 44-degree cut shutter, one of the oldest tricks in the book; it was the method used in the early days of television to archive live TV shows on film. The cut shutter eliminated the plasma flicker, but it also caused many of the LCDs to flicker. The only solution was to replace all the LCDs with models using more tolerant backlights. With the advances in digital compositing, some filmmakers are opting to shoot greenscreen instead of a live image on a monitor. Shooting a greenscreen eliminates the need to make an immediate decision on the content of the image, but it also limits the actors' ability to interact with the image. It also affects the scene's lighting: instead of featuring the corrected light emitted by the video screen, the scene is awash with a pale-green glow that appears on every reflective surface on the set. Of course, this green spill has to be removed in post. On Unstoppable (2010), the command center for the company responsible for the runaway train featured hundreds of flat-screen monitors. Director Tony Scott and cinematographer Ben Seres'm, BSC realized early on that greenscreen playback was out of the question because of the glass partitions jutting into the set from all angles. Tony prefers to use real locations and real technology when he can. (Let's face it: nothing looks more real than the real thing.) To achieve the look he wanted, Ben used a mix of sources, including Kino Flos and tungsten lamps, and because the monitors were featured in every shot, they were used as sources as well. Color correction was critical, and I spent many hours tweaking each monitor until everything had the proper balance, It worked well; nothing about the monitors looked unusual. The 24-frame video process has been utilized with great effect in many films, and it will likely continue to be a part of the creative process on many more. If your next project takes place in ancient Rome, you wouldn't think twice about the need for realistic wardrobe and set dressing. By the same token, if your story takes place in CIA headquarters or a broadcast-TV studio, why would you second-guess the value of realtime imagery? Left: Though their newness was appealing, large plasma screens proved problematic during camera tests for Enemy of the State, so the filmmakers chose to stick with older, reliable CRT technology for the movie's many onscreen monitors. Right: Just a few years earlier, LCD technology was used for a variety of small screens in Demolition Man. Right: To balance the color on all the plasma and LCD monitors featured on the bridge of the Enterprise in the latest Star Trek movie, the author displayed a gray-scale chart on each screen, then set the exposure and shot a test. In this photo, the gray scale appears on the row of LCD monitors, which are just below the plasmas. Below: A frame from the finished film shows the final effect. Monte S wann is the supervising engineer at Cygnet Video (Filmmakers' Forum, p. 84). (c) 2011 American Society of Cinematographers |