Where Have 3D Stereoscopic Movies Taken You?

February 26th, 2009 by Clint Posted in film | No Comments »

I can comfortably say that the range of quality of 3D cinema is almost as wide as the range of 2D cinema. Story and celebrity are still king. The introduction of digital 3D cinema seems to be an evolution more like the transition from 2 channel audio to 5 channel audio than the revolutions of sound and color.

The added dimension gives a better sense of scale. It provides another positional queue that can be used to manipulate the viewer’s immersion. Whether two or three dimensions per frame, films are still the filmmaker’s framing of the world through the window of the camera lens.

Technology Can’t Save A Bad Story

I saw a demo of Alioscopy’s auto-stereoscopic (no glasses needed) 3D display, which is a fancy plastic lens on top of an LCD. It actually works, but has a limited number of viewing angles, and requires an array of 8-10 cameras to create the video. I think this necessarily means the effective resolution is one-eighth to one-tenth of the LCD’s native capability.

I also saw a demo of 3D capabilities being built into some new LCD TVs at incredibly low cost. This wonderfully brings 3D into the home, and is claimed to be compatible with Sony’s high-def players. Neither of these techniques are practical for a theater though.

Turtles All The Way Down

The most popular projection technique for 3D is circular polarization, which maintains left/right channel separation extremely well, and is more robust at preserving color levels than linear polarization. The polarization is accomplished with a filter (linear polarizer mated with a magnetic field generator called a retardation plate) in front of the projector. The polarizer, which makes light coherent so the 3D trick works, is the death of brightness, killing over half (~60%) of the projector’s light. The light that gets through is spun clockwise or counter-clockwise depending on the electric field (+ to -, or – to +), which is switching at 144fps, or 6 times per frame. And then he 3D glasses take another 10% of the light. This is all fascinating to be sure, but if you’re switching a single image 6 times per frame to reverse the polarization, you’ve introduced 6 blanking periods.

Blanking periods are fine if they’re part of the media (like in a film projector), but when they’re introduced this way, you get unnatural motion that ghosts and stutters. This is noticeable (and distracting) in any scene with moderate motion – I bet snail documentaries look excellent. One published spec put the filter’s transition time in the blanking period at a very impressive .6ms, which means 3.6ms per frame, or 8.63% blackness as a conservative estimate, but I’d guess it’s closer to 15% in the end. A 2-projector setup isn’t unreasonable to help fix this, and maybe a 6-chip projector will work, but collimating light is a bitch.

A giant LED jumbotron will be even better if we can get consistent color. To make the 3D gag work, each pixel on the screen gets a clockwise or counter-clockwise polarizing filter. If you want to cling to the 4k wagon, then you’ll want an 8k display, but that seems excessive. “Modern” theaters are purpose-built facilities anyway, so why not ditch the silver screen?

“Because I Can” Isn’t Good Enough

3D has hit its stride is with computer-generated films, portraying a synthetic world through synthetic cameras. At The Conversation in Berkeley last year, DreamWorks’s John Batter showed us the Tai Lung escape scene from Kung Fu Panda, specially re-worked for 3D. It was great. John also said they carefully paced the depth effects because it easily becomes tiring, and scene transitions are carefully managed to prevent nausea. One of the more entertaining things I learned from him is that audiences don’t like to get poked, like with the pick-axe-in-the-eye gag that kicks off My Bloody Valentine. With that movie, the break of immersion caused by 3D gags was welcome, and maybe that wasn’t entirely accidental. An oddity worth remarking was the Superman “put on glasses now” scenes that were in 3D – bad idea.

One potential playground for 3D is aspect ratio games. Like the The Dark Knight IMAX (and a handful of other predecessors like More American Graffitti), we’re sure to see 2.35:1 frames being broken for added effect, because the mastering is really 16×9 (caveat projectionist).

The best use of 3D I’ve seen yet was in the awkwardly live BCS championship game. The 3D motion stutter is terrible for watching football, but you can easily grasp the relative sizes of the players in the huddle. One eye of the projection would regularly go haywire, followed by a full audience groan. One shot sang to me every time they used it: a deep-focus establishing shot all the way across the field from a corner of the end zone. The camera played the perfect role, melting away, leaving me wondering why I couldn’t smell the dirt on the field.

I Can Make A Plasticine Pancake

3D isn’t working for me in the claymation realm either. For Nightmare Before Christmas, 3D was added synthetically, and never felt like anything more than 2D cards floating around. With Coraline, the preview was nauseating because of the scene transitions, which luckily wasn’t a problem with the film. Deep-focus shots were again the most powerful, but most of the time the motion stutter was more distracting to me than the 3D was immersive.

Fix It In Post

Seam carving paired with re-projection is a candidate for making live action 3D as workable as computer-generated 3D is. Seam carving is a daunting task in two dimensions, but for many scenes, having stereoscopic pairs will help resolve features. You then rearrange the elements in 3D space, which brings you into the computer-generated arena, where a synthetic world and a synthetic camera are the ultimate in flexibility. The drawbacks to this approach include needing to capture at higher resolutions, and needing lots of light because you want to be stopping down your lens, aiming for the deepest focus possible. The more in focus the entire scene is, the more flexibility you have to adjust the virtual lenses during re-projection.

I Miss Captain EO

So far, story has been secondary to the technology with 3D films. This is almost predictable though, since the technical barriers to 3D are significant. Not only must filmmakers be fluent in the language of film, but they also need to blaze the trail in 3D production, inventing norms as they go. So far, only equipment manufacturers have seriously benefited. If anyone can make use of the immersive potential of 3D, it’s the likes of Steven Spielberg, James Cameron, and George Lucas, with brilliant crews and infinite resources to help tackle their problems. I can’t wait for the great storytellers to tell me another story. If they want to tell it to me in 3D, then so be it, but I don’t think it’s necessary.

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