There’s More To 3D Than Not Having To Say Sorry!
Posted on Mar 26, 2010 by Alex Fice
I was quoted, in a recent issue of this magazine, criticizing the methods of live-action stereo capture as advocated by Messrs. Pace and Cameron with Avatar, specifically their choice of slaving convergence to focus. Whilst I maintain the view that stereo anomalies will occur and are in evidence in some of Avatar’s live action sequences as a consequence of shooting this way, I felt a little shocked and embarrassed by the sheer venom my opinion was laced with by the time it was expressed in print. True, I personally wouldn’t choose to shoot this way, but in the grand scheme of things, who am I to appoint myself grand inquisitor and condemn it as 3D heresy? There is no one single right and correct way to shoot stereo, there are only preferences, and I’m clarifying this because the whole point of this article is to promote an understanding of ‘Stereography’ as a creative discipline, rather than a solely technical one, which is kind of untenable if I am known to have first thrown all subjectivity out the window. The glorious and beautiful reality is that 3D production is so very much dependent upon what your stereo objectives are from the outset, and upon what the audiences’ 3D expectations are of your film, which of course is tied into genre and a myriad of other creative and practical factors that will all duly colour your stereo choices and application thereof.
Of course, there are some absolute rules and conditions you would be well advised not to violate, that is, unless in the spirit of Dali and Buñuel perhaps, your objectives are so avant-garde that you actually wish for the viewer to throw up. But good 3D must surely be measured by more than creating the perception of depth whilst successfully keeping everybody’s food down?
Yes it is generally and rightly accepted that good 3D is, first and foremost, comfortable to watch! It immerses us in the story world and it helps reinforce the suspension of disbelief, both within a narrative context, and in the context of attendance, such as the sensation of actually being at a 3D concert or sporting event, for instance. Good 3D therefore draws no attention to itself. If the viewer is forced to look away because of discomfort, or is equally disengaged by stereo-show-boating, then you have in both instances betrayed the requirements of your story and made the viewer cognitive of its processes. Just because you can hurl a javelin into the viewers’ forehead, doesn’t mean that you necessarily should. It doesn’t mean that you necessarily shouldn’t explore and exploit negative-Z depth (out of screen functionality) options either, provided it is not clichéd, but more on this later.
3D is no different from any of the other technical disciplines that in concert, and with creative application, make motion pictures, so do let’s get the science of it into realistic perspective. We would all generally accept that extensive training and a relatively acute mind is required of a Director of Photography or a Visual Effects Supervisor, and if these skill-sets were scant and not so widely understood, as is the case with stereography, then they too would probably be scrutinized with similar measures of both reverence and skepticism. Despite the technical knowledge required of a DoP, we still tend to speak of them in artistic terms, distinguishing the good from the bad by their levels of invention and ability to paint with shades of light and colour. A stereographer should be defined similarly in their ability to manipulate and control depth for dramatic effect, because just as the art of lighting is so much more than insuring everything is correctly exposed, so too the art of 3D is so much more than just adding dimension and comfort to a shot.
3D simply doesn’t operate on a one size fits all setting. Sure, you will most likely set and fall back on a global operating level, but this should dial up and dial down dynamically throughout your story and even within an individual shot if there’s a dramatic requirement for it. Let’s say I was shooting a prison break, for example. I might very well want to dial down my stereo in the beginning, compress the space because I want a heightened sense of claustrophobia and oppression inside the prison cell or escape tunnel. Once my jailbird takes flight and is out in the open, drinking in the sun and clean air, I might open up my depth budget and swallow him up in an expanse of space to accentuate a sense of freedom or even agoraphobia if it was relevant, and thus, potentially increase the dramatic payoff of this sequence.
Okay, this is a very basic example, but a pretty effective one for illustrating how the manipulation of depth can serve a dramatic purpose, aside from just endowing your story world with dimensionality.
And there are many ways to manipulate or personalize the perception of depth. Setting interaxial and/or convergence, is not, nor should it be, your first consideration. Setting your scene and your action should always be the priority and this will then in turn inform you how to set up your camera system. Your internal action and camera moves will in themselves have a bearing on the perception of depth. How is the space utilized in shot? Might it best serve your stereo expectations and support action to dolly through space i.e. along the z-axis rather than across the scene?
Consider that stereopsis, our ability to see the world three dimensionally, is only one of many ways in which we reference and register depth in our daily lives. We also use motion parallax, perspective, and scale, to list but a few, not forgetting atmospherics (The lunar astronauts expressed great difficulty judging distance on the moon because zero atmosphere meant that a mountain range on the horizon had the same visual sharpness and clarity as a boulder only meters away) and we should also remember that sound informs our perception of depth too, for example, the Doppler Effect. All these alternative and additional depth queues can be added to the filmmaker’s stereo palette and be employed in varying degrees to enhance our immersion and perception of volume and space. Conversely, they might also be consciously omitted to collapse it.
Avoid un-watchable 3D
3D therefore has some very specific requirements of composition and framing, which in turn impacts the blocking of action, which of course effects camera moves and shot duration. There is a tendency, certainly with film action sequences, music videos and commercials to significantly exceed the shot count actually required to deliver the intended message or exposition. This is done in the most part to maintain visual interest and keep modern audiences engaged. But any rapid shot assembly of this nature, particularly coupled with agitated camera moves will most definitely create unwatchable 3D, certainly so for the big screen, to a lesser extent on television, but the ‘keep it comfortable’ rule will nevertheless be violated. When you watch a 2D movie your eyes are more or less set on a single point of focus and convergence, which is the actual screen surface on which the movie is projected. Your eyes are only ever likely to shift focus and convergence when you look down having spilled your pop corn, or turn around to scowl at the person who left their mobile on. When you’re watching stereo content, however, your eyes are literally interfacing with the film world the same way that they would interface with the real world. In the real world, our eyes of course adjust focus and convergence as we shift from one point of interest to another. It is a physical muscular activity conducted over time, and regardless of how imperceptible this action and its duration may seem, our eyes simply do not snap from one state of rest to another instantaneously, which is precisely what a rapid shot assembly would be asking them to do. By bombarding the viewer with visual stimulus and information in such a way, you literally overload their physical capacity to view and process that same material. Ironic hey! Which is why it is also good practice, even with a more languid pace, to still balance your stereo across the cut i.e., shift your entire depth budget along the z-axis so that the stereo from one shot to the next meets at a convenient and comfortable middle ground during shot transition. Something that is infinitely easier to do, if you have plotted your stereo properly from the outset. The implication anyway, certainly for 3D production is that film grammar is going to have to shift from a reliance on this visual shorthand or patois, to a singularly more concise vernacular! In other words, longer shots individually stacked with more information. The good news though is that dimensionality inherently adds visual interest to a shot and audiences tend to want to have a little more time to explore and savour the eye candy you pack into it. Additionally, it is my experience that the same shot in 3D generally feels faster and more dynamic than when viewed in 2D and I suspect, although admittedly I am no neurosurgeon, that this is down to a certain degree of latency within the brain while handling stereo tasks – it simply requires more processing power to do it.
Anyway, with all this in mind, producers should be encouraged to couple their director with a stereographer at the earliest stage of pre-production, so that between them they can identify where and how variations in depth might serve the narrative, flag situations that are likely to create edge violations and reveal where compositing might even be required to meet stereo expectations. Ideally you should really be able to graphically chart your depth budget throughout your entire project, be it a movie or music video, follow its undulations, and peaks and troughs, as they correspond to variations in the action, drama, suspense, melody and choreography. The point is, your 3D considerations and awareness should not be starting on the first day of principle photography, based on the assumption that the shaman with the beam-splitter will just cast his stereo voodoo over everything and that’ll be the end of it. If you want your stereo bespoke and fashioned in your own image, I would even advise you to go and learn the basic principles for yourself, because although you can hire the technical crew and shoot in 3D tomorrow, until you are working from a wholly informed position, until you know how to exploit the rules and their loop-holes for yourself, you are likely miss a trick, and nobble your full creative potential.
3D is a wholly subjective process! If you need further evidence of this, then consider how fashionable it is right now to stigmatize the employment of off-screen effects. Apparently it has no relevance to modern 3D cinema and all instances of it should be tarred with the same gimmick brush. I’m not about to endorse a cheap poke in the eye with a long stick, don’t get me wrong, but, as I have been trying to qualify from the outset, stereography is the art of impacting or underscoring the viewers’ emotional engagement with the story through variations in perceptible depth, geometry and yes, even proximity. So, with this I fire my parting shot and very unfashionably maintain that if it is narrative driven and heightens the audiences’ emotional engagement with the scene without pulling them out from the story, then absolutely, why shouldn’t you have the occasional and very cool off-screen effect? Do you really think all those people sitting in the auditorium with dark glasses on have absolutely no expectation of this at all? Choosing to sneer at this simply as a backlash to old corny gimmicks is to voluntarily hamstring your productions’ full 3D potential and inadvertently admit you lack the invention to make such effects anything but cheap. Well that’s my humble and subjective take on the matter anyway.