Just something I wrote for AnimationSa.org as an Opinion Piece on Stereoscopy… thought I would put a copy up on my blog too.
I have a confession. I am a stereographer who doesn’t watch 3D movies….well Live Action ones that is. Not because the content, visual effects, or story are particularly bad, but because I am bound to walk away feeling a little despondent about the field in which I work. Stereoscopic imaging may not be new to the film world having been around since the ’60s, but unfortunately the Live Action guys have so many physical constraints that directly influence their final stereo footage. So let me preface this by saying, of course I am biased… chances are everyone reading this on AnimationSA.org will join in behind me and agree, simply because, well, we’re all in Animation!
For those new to stereoscopic cinema, at its simplest we film the same movie twice once for your left eye, and once for your right. Obviously there is a lot more to it than just that… but that’s all you’ll need to know to understand most of the issues that Live Action suffer from. In a CG environment we have a better than ‘perfect world’ no dust, minute accuracy, and best of all no physical constraints (our cameras can sit inside each other). The average humans eyes are separated by roughly 65mm, no two Cinema Cameras are small enough to have the centre of their lenses 65mm apart thus most commonly Live Action will shoot through a mirror rig (or beam splitter) where one camera films straight like normal, but through a mirror and another films down reflecting off the mirror. This is just the start of their issues, these rigs do their best to make camera alignment as accurate as possible but often small geometric distortions occur, keystoning, rotational, zoom difference between cameras can instantly create stereoscopic problems. You say what’s a pixel or two disparity (differences between left & right eye) between friends, I say, ‘Work out the mathematics of 4pixels magnified to an average 40ft (12m) screen!’ Basically its like having a something the size of a match box thrown at your face and only hitting you in the one eye! Cinema projection is all about magnification, ‘always better on the big screen’?!?
Lets dig deeper, disparities in all their incarnations I believe are the gradual causes of headaches and eye fatigue during a film. Geometric distortions are just the beginning. Transformers 3 was riddled with reflections in cars often being brighter in one eye than in the other, specular hot spots on actors faces (also reflections) being visible only to one camera and not to the other! Subtle colour variations between eyes can also become a problem along with lens artifacts like lens flares, etc are all potential stereoscopic problem areas.
I would hate to see a sunset shot over the ocean filmed in stereo, all those little reflections would be a nightmare. Technically it is these disparities between eyes that actually makes the ocean look like the twinkling diamonds you expect to see in real life. The human brain has learnt to accept these disparities as normal, but when they are captured and transferred to film our brain is less accepting of them.
The benefits to animation are obvious we get so much for free, never bothered by colour variations, geometric distortions, rotational or zoom differences, that’s well over 75% of our way to a perfect stereo pair. Dreamworks committed to a fully stereoscopic workflow years ago and their movies are real evidence of excellent use of 3D. We sadly don’t escape scott free! Gnomeo and Juliet had a few shots in the long grass where the thin blades didn’t quite match up in left and right frame. Pixel size disparities are a constant curse (ask any one of the compositing artists that work at Triggerfish Animation Studios) often a small bright spot between two leaves (on the tree of Zambezia) will only be visible in a single eye and so we send in a compositor to clean up the disparity. Like any good criminal knows, you have to clean up the scene of the crime
There is a whole other and further discussion to be had from the fact that in Animation we can preview our entire environment in 3D before going to render. We can position objects and adjust our stereo depth bracket as we see fit based on every unique shot. At the end of the day Animated films are bound to have better stereo than live action. The odds are just generally stacked against live action, and that leaves the door wide open for us lucky few placed in the prime location of 3D Animation.