Friday, December 18th, 2009
Over the last several days I've been pouring over the reviews of Avatar, hoping to find one that offered an in depth analysis of the stereoscopic quality. I haven't found one yet, so I decided to write at least a basic one. Tonight I watched the movie twice - first using Real-D technology, and second (and immediately after) in IMAX 3D. I expected the Real-D experience to be better due to the following (perhaps gross) assumptions:
Installed base of Real-D (or equivalent) driven screens is higher than that of IMAX, so I was hoping that it more closely matched the studio development setup (assuming the studio targeted the tech with the highest market penetration).
Generic stadium seating + native aspect ratio and scaling can provide a more ideal stereo viewing ratio (defined as the display size in meters divided by the viewing distance). In other words, stretching the image, while potentially forcing viewers to sit closer to the screen, is not a winning combination.
My own personal preference (granted, not really an assumption :)) for circularly polarized filters, and the comfort of Real-D glasses.
Granted, these assumptions aren't on the most stable ground, but they nonetheless drove my decision to view the film in a Real-D format first. Assumption two may require a slightly longer explanation, but suffice it to say that in an ideal world you would be seated orthogonally to the screen, and view content that was specifically calibrated for your display size and viewing distance. Viewers may notice that they perceive a very different experience in the front row than that perceived from the last row.
My decision proved to be a wise one, as the quality of 3D appeared to be noticeably better with Real-D. I did however find that both sets of glasses were very uncomfortable, especially towards the end of a two and a half hour movie.
The film appeared to be very well received by both audiences, and it received a standing ovation at the credits. A few people moved around the theatre to get a better view, but I didn't notice anyone taking the glasses off or showing any strong visible signs of discomfort. The first 3D trailer shown was for the new Alice in Wonderland movie - and the quality of the stereo calibration seemed extremely poor. Due to the persistent nature of fatigue, I'm not sure that showing this trailer was a wise decision.
During the first few 3D scenes of Avatar there were a large number of audible awes and gasps. Eventually these subsided as people seemed to become more engrossed by the film (although the 3D remains a dominant part of the experience throughout). On a side note, the Real-D filters on the glasses I used are very easy to remove and re-attach. I would suggest that any couples who feel discomfort from the movie may want to try swapping filters to pair a left with a left, and a right with a right, in order to continue watching the rest of the film in the comfort of 2D.
It is clear that this movie was conceived and produced to be a premier 3D experience. Avatar represents some of the best and most spectacular stereoscopic footage I have ever seen - however it is not without its flaws. The initial portions of the film are dominated by live action footage, while the later portions are primarily computer generated - and this is significant because most of the live action was difficult to watch, while the rendered scenes were often breathtaking. The technologies used for these components are similar, but noticeably different, and it has a dramatic effect on the film.
Filming in live action stereo is a daunting task - especially when filming simultaneously for both 2D and 3D. Many of the classic filmmaking techniques become unavailable, and are replaced with an entirely new set. Avatar's direction (particularly in CG sequences) clearly shows a strong understanding of 3D filmmaking, and certainly deserves recognition. That said, critical evaluation is an important part of the process of evolving this new format. I am still in the process of reviewing and formulating my notes, but here are a couple brief highlights:
Specular Highlights and Umbrae
It is generally wise to avoid severe color contrast on hyper-stereo objects. The best example in Avatar's live action shots is the abundance of surfaces exhibiting bright specular highlights adjacent to soft and dark shadows. Faces in particular are difficult, due to their curvature, because each eye is likely to see slightly divergent sets of information. When a viewer's eyes perceive a strong brightness delta along a very stark boundary, it becomes very difficult (and uncomfortable) to resolve the discrepancy.
Figure 1: The uniformity across the characters face makes it very clear and easily in focus. The intense highlight on the helicopter in the background however, is very difficult (and fatigue inducing) to bring into focus.
A frame violation occurs when objects that intersect the edge of the frame (partially off-camera) appear to be closer to the audience than the screen. This will produce a very uncomfortable experience as the brain attempts to rectify divergent stereo cues. Surprisingly, Avatar exhibits this issue fairly frequently in the live action footage, but far less frequently (or at least less noticeably) in the rendered shots. I did not notice any use of floating windows (ala Bolt 3D) anywhere in the film.
The majority of the live action scenes appeared to utilize a toe-in camera configuration, and as expected, the focal depth is changed fairly regularly within a scene in order to maintain focus on an object of interest (usually the speaking character). This is often problematic in the film because it induces fatigue whenever a viewer focuses on something other than what the director would prefer. Additionally, the depth ranges traversed through slow racking focuses are often great enough to further induce fatigue.
Many of the environments of Avatar (most notably the Marine bases) are extremely complex, with dense foregrounds. Insignificant characters, furniture, computer monitors, and other foreground objects are often in motion and impossibly difficult to focus (further inducing nausea and/or fatigue).
Focal Depth Preservation
Many of the cuts in Avatar do not preserve the focal depth, which forces the viewer to quickly adjust focus for the new scene. In situations where the depth can be preserved across a cut, and makes sense (particularly if a sound bridge is present), I would expect to find a depth bridge.
Stereoscopic camera motion is particularly difficult due to the high potential for inducing nausea. A number of scenes in Avatar contained rapid rotations combined with some degree of camera translation, which felt uncomfortable.
Throughout most of the film it is clear that the viewer's gaze is controlled through depth cues, lighting cues, etc. This becomes problematic however, as viewers wish to fully explore the lush 3D environments being presented. Those who step outside the boundaries in any given frame are rewarded with discomfort from trying to bring an object into focus that isn't the intended object of interest. This is undoubtedly deliberate, but my personal preference is to favor comfort over control wherever possible.
Despite these issues, the film delivers on a number of stereoscopic achievements. Firstly, the film utilizes depth as an emotional device. The clearest examples of this are found in scenes with broad open and expansive vistas and scenes where the main character teeters on the edge of a cliff. Depth is further used to heighten anxiety during a pursuit, or to draw the audience in to a character. Additionally, depth queues during a number of emotional sequences between the primary characters add a subtle but meaningful effect.
Cameron also effectively uses brightness to enhance (or minimize) the stereoscopic effect. The lush forest environments assist the experience, while the subtle darkening of objects approaching the extreme foreground help to minimize ill effects of extreme stereo separation. Perhaps the best combination of brightness, emotional depth, and proper object movement relative to separation is found in the wisp-like seeds that periodically dance around the main character. Audience members in both showings were audibly pleased with the playful appearance and nature of these objects, and their crisp stereo delivery seemed to heighten the effect.
Without a doubt, Avatar has advanced the art of stereoscopic filmmaking. It delivers a compelling experience that spans a wide gamut of stereoscopic techniques. It is not however without its flaws -- many of which induce fatigue and discomfort. So much of this process is subjective, so I do not doubt that many of the flaws I have perceived were meticulously implemented for this film. That said, the world is still in the process of converging on the proper set of techniques and practices for stereoscopic filmmaking, so this discussion certainly bears merit. In the end I believe that history will likely view Avatar as an important step towards the future of stereoscopic filmmaking, but not necessarily a testament to its arrival.
Comments, questions, concerns are always welcome. Please note that these views are not necessarily those of any of my affiliates. If I do not get around to posting more of my notes (in particular the ones that would require a lot more explanation), please feel free to email me for a copy.
Thanks for reading!