In the Eyes of the Beholder

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Thu, 08/27/2009 - 20:00 -- Nick Dager

Thanks to the recent advanced screenings of some fifteen minutes of director James Cameron’s highly anticipated release of Avatar in stereoscopic 3D the movie world is buzzing in chat rooms all across the Internet about the event and about 3D in general. This makes a new report from the Gerson Lehrman Group all the more timely. Their report outlines the very real physiological challenges caused to the human eye and brain by stereoscopic 3D challenges that must be understood by manufacturers moviemakers exhibitors and movie viewers alike. The Gerson Lehrman Group established in 1998 maintains a council of networks of consultants physicians scientists engineers attorneys market researchers and other professionals from around the world. Council members according to the company “Leverage GLG's sophisticated proprietary systems to categorize their experience and expertise. GLG research professionals use these systems to quickly provide relevant council members who can help clients better understand products services companies issues and industries.” Full disclosure: I am a member of the GLG Council and working with them I have consulted with several companies interested in digital cinema. However I was not involved in the 3D report described here. As their report says there are serious issues related to the physiology and psychology of human vision when a person experiences motion pictures in digital stereoscopic 3D.  One is called the infinity-interpupillary problem; another is the accommodation-convergence problem. The reactions to the Avatar screening were decidedly mixed around the world although from a marketing standpoint the event would seem to have been a success. Most reports described the audience reactions as generally positive and most attendees I saw quoted said they would definitely see the full feature when it is released later this year. I was not able to get tickets to the screening; they sold out too fast. In her report on the Avatar screening Annlee Ellingson editor of Moving Picture Magazine touched on some of her physical responses to the movie. “But when there's a lot of quick movement – as in the fast and furious action scenes – the 3D causes vertigo and eyestrain ” Ellingson wrote. “Some viewers may consider the vertigo a plus enhancing their experience of being part of the action. However while the eyestrain subsided by the end of the presentation it remains to be seen whether achy eyeballs will be alleviated or aggravated by a feature-length run time.” According to the GLG report there could be real factors that contributed to Ellingson’s eyestrain. The infinity-interpupillary problem relates to the way we see distant objects or scenes with our eyes pointing straight ahead.  To match that a 3D display should have those objects at the same spacing – roughly 2.5 inches apart.  That's easy to achieve on almost any screen from a TV set to a movie palace.  Unfortunately points that are 2.5 inches apart on a TV screen will be much farther apart on a movie screen demanding our eyes to try to diverge an unnatural condition.  Conversely points that are 2.5 inches apart on a movie screen will be much closer on a TV screen giving the impression that distant objects are much closer as though the viewer had the eyes of an office-building-sized giant.  And on a mobile-phone screen the 2.5-inch spacing could be simply impossible. The accommodation-convergence problem relates to human-visual feedback mechanisms associated with lens focus in the eyes (accommodation) and the angle at which they point (convergence).  In the real world the two are locked together.  In most forms of 3D (holography is an exception) the convergence might be in front of the screen or behind it whereas the accommodation is always at the screen distance.  Professor Martin Banks of the University of California in Berkeley presented evidence to the 2009 Digital Cinema Summit in April that the accommodation-convergence problem can cause physical discomfort. Banks and a team of graduate students in California and at New York University have been studying this for years. While much has been learned the study continues. In his April presentation Banks suggested that moviegoers should be encouraged to sit in the center third of a movie theatre to get the optimum 3D experience. Those sitting in seats to either side may have little to no 3D experience. He also suggested that two people sitting side-by-side in a theatre could (and possibly always will) have a completely different 3D experience because everyone “sees” 3D uniquely. In an effort to hear more experiences about stereoscopic 3D in general and the recent Avatar screening in particular I posted this question to Digital Cinema Report groups I run on two social media sites: “I could not get tickets to the Avatar preview screening last week but I've read at least one credible report by a journalist who got eyestrain from the action scenes in 3D. Was this experience a unique one or did you or someone you know also have the same response?” James Hyder the editor of LF Magazine and an authority on giant screen technology answered this way: “If you've seen Cameron's Ghosts of the Abyss or Aliens of the Deep you know that he likes to slave convergence to focus. This works okay with conventional digital 3D where most depth is behind the screen but IMAX's concept of 3D has always been parallel convergence. This may have accounted for [some] eyestrain. “Even though I saw the preview on a small IMAX digital screen I found some of the camera motions too fast for comfort. Cameron is apparently unaware of Ben Shedd's maxim that when making an IMAX film you don't pan the camera you turn the theatre. That is to the viewer camera motions feel like the theatre is moving. So a hand-held shot feels like the whole theatre is shaking. There were a couple of very uncomfortable handheld shots in Ghosts of the Abyss and a few too-rapid pans in the Avatar preview.” Bryant Frazer editor of Film & Video magazine and a respected movie critic with his own website Deep Focus is also a member of one of my groups and he said this: “I didn't see the Avatar preview but 3D movies always give me mild eyestrain. The only question is whether 15 minutes would have been long enough for it to bug me. I put up with it because it's cool technology but I wouldn't want to see a 3D movie every week.” None of these problems is necessarily insurmountable. History has taught us that human beings have an innate ability to adapt to new things. Human perception can be trained.  As the GLG report notes when the Lumiere brothers showed a black-and-white silent movie of a train in 1895 a contemporary account suggested that at least one audience member feared there was a locomotive in the room and adds that long before high fidelity a reporter for the Pittsburgh Post said he was unable to tell the difference between an Edison phonograph recording of an opera singer and the real thing. The point is more study about the effects of digital stereoscopic 3D on the human eye needs to be done but perhaps we’ll simply adjust over time. The GLG report concludes by saying “Perhaps we can be trained to deal with the infinity-interpupillary and accommodation-convergence problems too. But the long-term success of 3D as more than a novel gimmick alas will require more than shooting transmission and stereoscopic-display developments.”