The Myth of 3D.03 Jul 2010
There's a lot of hype these days about the emergence of 3D and its effect on the box office. Various people, including the esteemed Roger Ebert, have claimed it is a gimmick and a fad. Let me just state, first off, that I agree. There, I've set out my stall. Now I will attempt to explain why I think that way.
We perceive three dimensions through a variety of mechanisms, all of them contained within the brain. First and foremost, we recognize the depth relationships of an object based on our understanding of it. If we look at a two-dimensional photograph of a car, we know that the rear bumper is at the back, the headlights are at the front, and so on. We understand the relationships of these parts to the whole thing and we don't need to perceive depth when we look at it. Except, of course, for the first time we see a car. Second, we interpret the horizon, or the "vanishing point" and perceive depth through that. When we look at a road or railway tracks stretching out in front of us, our brain interprets the convergence of the edges as distance. As the road stretches to infinity, the sides of the road come together to a single point.
As an experiment, sit on the floor in front of a rectangular rug. Sit nearest one of the shorter edges. The rug appears rectangular. But either take a photograph, or look at it objectively. The short edge nearest us is actually longer in our perception (and that of the camera) than the edge furthest away. Again, our brain performs the transformation and lets us see a rectangular rug but appreciates that it has depth. When we look objectively, we see what our eye sees. However, most of the time, our brain performs the translation for us.
This is one of the most commonly-used cinematic methods for showing depth. We can also fool it. For example, in the final shots of Casablanca, both the model aircraft and people attending to them, are smaller than normal, but our brain interprets this to mean they are further away. Also, the streets in the Old West section (now gone) of the Warner Brothers back-lot in Hollywood, converged on each other. The buildings at either end were smaller, so that when you shot a scene in the middle of the street, it appeared longer than it actually was.
Another effect the brain uses to determine depth, is to interpret haze. Water moisture in the environment forms a haze, which "washes out" the image. The vivid colours of mountains in the foreground contrast with the paler colours of hills further away. Artists have been using this phenomenon for centuries, to depict depth.
However, one of the most important mechanisms for establishing depth is our ability to interpret the movement of objects as we move. Hence the "tracking shot" in almost every film. When we look out the window of a car or train, the telephone poles shoot past at speed, whereas the faraway hills don't seem to move much at all. Again our brain interprets this relative motion and deduces the relative positioning of the objects, in terms of which is closer. Animators rely heavily on this phenomenon to achieve depth in their films. As we track in during the opening sequence of The Simpsons, the clouds part at different speeds, making us think that some of the clouds are closer than others.
Shooting a scene in a warehouse, if we open up with a dolly shot, tracking through the scene and observing our key players, we are subconsciously explaining to our audience, where everyone is, in relation to each other. The concrete pillar which whips past is probably quite close (it's also out of focus which helps, as well). The guy by the exit door doesn't seem to track left or right, so he's probably further away than we thought.
Focus is also important for establishing depth. Film-makers love 35mm cameras and lenses not just because of the organic nature of the image, but because the depth of field can be quite narrow. Objects further away are progressively more and more out of focus. We can use this not just to draw the viewers attention to the key point of the scene, but to show the depth as well. To highlight the spatial relationships for the dimension that the camera can't show.
Finally, we come to stereo-vision. We have two eyes, spaced about 3 to 4 inches apart. For objects which appear in our immediate field of view, neither eye sees exactly the same thing. Their perspective is skewed. Again, our brain realigns this image, forming a picture which does not show the duality and instead interprets the difference and thus the depth.
So, why then if we have so many ways as storytellers, to portray depth in a scene, must we use the ugly mechanism of twin cameras shooting through filters? The difference between what one eye sees and what the other sees, is highly proportional to the distance between us an the object. So, if our intention is to portray a character appearing mere feet or inches from our face, stereo-vision is highly effective. However, most often when we are trying to portray depth, we are talking in terms of objects which are farther away from us. Try this experiment. Observe a three-dimensional object (such as a box) which is some distance from you. Close one eye, then the other. Do you see much of a difference? Is the perspective all that different between your two eyes? A stereoscopic film camera won't see much difference, either.
So why, all of a sudden, has a technology which had its heyday in the fifties, reappeared? Why has this strange form of storytelling re-emerged after it was ridiculed and cast into the bin of filmic fads. One thing that is different now, is the emergence of digital cinema. The nice people at SMPTE have devised a digital representation for a motion picture, called a DCP (for Digital Cinema Print) which encapsulates all of the information of a 35mm film negative, at a bit rate of 250Mbps. In other words, a feature-length film can be saved onto a 250GB hard drive and played out from that drive onto a film screen, using a digital projector, without any noticeable loss in quality. Quite the opposite, in fact. Gone are the "dish" marks, the tram-lines, the splices, and other damage that we've come to expect from films once they've been in the theatre for a week or two. In fact, a DCP will project as well as the best print of the film. Assuming, of course, that the cinema has been properly calibrated.
While that's all well and good, the real advantage to DCP lies in an unexpected benefit; ease of duplication. Lest anyone think this can be pirated, the files are encrypted using AES and the keys are different for each film print. Not that long ago, a film going on a very wide release on its opening weekend, would appear on 2,000 or so screens. Today, it's not uncommon for a film to open on over 4,000 screens. Given that a film print can cost between $2,000 and $4,000 to make, not to mention the fact that a feature film would normally be distributed on six large and bulky film reels, the advantage of being able to copy files onto a small hard drive and put it in the post is immediately obvious. The long-term plan would be to use satellite distribution so that the film can be downloaded to cinemas across the United States, and around the world even, in one fell swoop. Digitally, and at little cost (apart from Satellite traffic costs).
A new dawn for cinema. Particularly for smaller distribution companies and independent cinema, as the prohibitive print costs are eliminated. I'll save the discussion of advertising costs for a later day.
The down side however, is that a digital cinema projection system can cost around $100,000 to install. Guess who pays for this? The cinema owner. Also, a 35mm projector is an oddly simple device. It hasn't changed much in a hundred years. The upshot of this is that if the projector stops working, the cinema owner can fix it from parts he or she probably keeps in a desk drawer. The technology is easily-understood and easy to repair. Not so digital cinema. The projector itself is an expensive, high-tech behemoth. It is driven by a playout server, most likely running Linux (the DCP disk format is EXT2 for those of you who know what that means), the files are encrypted using AES and the keys must be delivered separately for each projector in each cinema. This is also combined with something called a "Theatre Management System" which co-ordinates the playout systems, the advertising, the ticket sales, and the key management. Is it any wonder that theatre owners are less than thrilled by digital cinema.
To counteract the costs involved, the US distributors invented a scheme called the "Virtual Print Fee" (VPF) where they pay an agreed amount to the theatre owner for each film they screen digitally. In effect, the distributor passes on some of the cost savings from the DCP to the theatre owner to offset the cost of the projection system. This has allowed theatre owners to borrow funds to pay for the capital costs against this fee. The uptake has been significant, but hardly stellar.
Most cinemas have adopted a "wait and see" approach, converting one or two screens to digital and leaving the rest with traditional projectors. This has caused additional and unexpected problems. Traditionally, cinemas open the big films on their largest screen and as demand tapers off, they switch the film to a smaller screen, freeing the large theatre for the next tent pole. However, this is impossible if the film was shipped digitally and only the large screen is digital. This has required some distributors to ship both DCP drives and film prints. There are also key (KDM) issues because the key to un-encrypt the digital print is valid for only one playout system and projector. To move the film, say, from Screen 1 to Screen 5 would require a new KDM file from the distributor. While it is a small file and can be readily emailed, it's hard to make last-minute changes which removes a level of control from the theatre owner.
For all these reasons, theatre owners have been reluctant to jump on the bandwagon, even if the studios and the distributors love the idea of a DCP.
Interestingly, the new 3D technology at work involves using polarized filters on the viewing glasses. The old technique was to use red and green filters, or cyan and magenta filters. Instead of combining the two images into the same frame as was done with the colour separation form of 3D, the frame rate is doubled from 24 frames per second to 48fps. One frame for the left eye, and one frame for the right. Guess what! Film projectors can't run at this speed and cannot project a polarized image. The only way to show a 3D film on general release today, is to use a DCP and to project it digitally.
Which means, if you want to show Toy Story 3 in 3D on your main screen, that screen needs a digital projector. With most of the tentpole films now being released in 3D, if you want to keep your customers, you'll invest in a digital projector, regardless of your concerns about the VPF or the technology itself.
As an added bonus, 3D films have a higher ticket price which means the kick-back to the theatre owner is larger, as well. Not to mention the VPF.
Now, I'm not saying that films like Avatar were made in order to promote digital cinema, but it can't hurt to have it as a 3D film. Even the latest film from M. Night Shylaman, called The Last Airbender, is being released in 3D even though it was shot using a traditional 2D process. This awkward conversion to 3D during post-production is generally frowned upon, but popular nonetheless.
We can expect all tent poles from Avatar to Pirates of the Caribbean and everything in between to be released in 3D for the foreseeable future, until the studios think they have critical mass in terms of digital cinema. Hopefully then, they'll relegate it back to the film fad dustbin and we can enjoy storytelling without the annoying glasses, or headaches.