hopinet

3D cinema, really?

5th May 2010

After seeing Avatar instead of reviewing the movie as that had been done to death already round the web I thought I’d look at 3D cinema, how it works and how you eyes interpret what they are seeing. A month on I’ve now got round to writing the post I meant to ages ago.

3D cinema has been around for a while now but it has been only used in specialized circumstances, now with digital projection and other new technology it is trying to break through into the main stream. Before I get going on how it works, I just want to say I still don’t get the fascination with 3D cinema, I’m not a big fan. Can we not tell a story anymore, do we need to hide behind all the smoke and mirrors of CGI, big special effects? I just feel 3D is just another technology we can use instead of actually making a good film with an interesting plot. I will keep going to the cinema if you make good movies, I don’t care if it’s black and white, 4:3, 12.1 surround sound or whatever, make a good movie and I’ll keep watching. Anyway, enough of my moaning how does this 3D stuff work?

Nowadays, 3D films arrive to the cinema on a big hard drive, this is plugged into the digital projector and then a special adapter fits onto the front of a single projector to separate the left and right images. In the case of RealD (which is the chosen format at my cinema and seems to be the most common method, though there are other methods) this adapter is a circularly polarized liquid crystal filter and switches polarity 144 times a second, just one projector is used and so the left and right images are displayed alternatively, obviously so fast we can’t perceive it. The wearer then wears the pair of polarized glasses so each eye sees the appropriate image. I’m sure that’s as clear as mud!

So I’ll try and start with the basics and try and keep it fairly simple but I’m going to warn you this could get complicated quite quickly. Basically light travels in waves, exactly like the waves in water, however unlike a wave in water, light waves travel in all directions. A polarizing filter only allows light through that travels in one direction, so for instance only light traveling in a vertical wave. Lets say that this is the left eye image, the filter then lets the light through that is traveling in a horizontal wave, this is the right eye image. This filter flickers between the left and right image, because it flickers so fast our eye can’t detect it and it looks like a continuous image. The glasses that are then worn by the viewer then also have polarizing filters in to allow the appropriate wave through and so each eye sees the appropriate image. If you take your glasses off during a 3D film you will see what looks like a blurry image, this is in fact the two images superimposed on one another on the one screen. It’s a blurry image as they are in slight different positions, which brings me nicely on to creating the 3D experience.

Just because you have these two separate images doesn’t mean you have a 3D image, you have to do something else. Basically separate them horizontally, the more the images are split the closer (or further away if you cross the images the other way) the 3D image will appear. It’s the same principle that was used for those magic eye pictures that were all the rage 10 years ago. This works because the brain works out how close/far things are by interpreting the slightly different image our left and right eye get of the world, because there is a gap between the eyes we can do this. Try closing one eye and then try and catch a (soft) ball or place you arms in front of you and point each of your index fingers at each one and then try and line them up, it’s hard!! Basically, 3D abuses this to trick our brain into thinking things are in different places by falsely creating this slight different image for the left and right eye.

We now know the theory of what we want, well how do we create it. In very simple terms there are 2 methods really. Either film using two cameras which are separated like our eyes, this would be how I would do it to get the best results but it means twice as much film is need, twice as much camera equipment and a lot more expense. The second way is you fake it using computers, cheaper, but it just won’t give a natural result (in my opinion) and I’m not the only one, Variety recently talked to Jeffrey Katzenberg, CEO of DreamWorks Animation, about the state of 3D film making. He said “all 3D is not created equal.”, I don’t think he was a fan of the work done on Clash of the Titans “We’ve seen the highest end of (3D) in “Avatar” and you have now witnessed the lowest end of it (in “Titans”) You cannot do anything that is of a lower grade and a lower quality [3D] than what has just been done on “Clash of the Titans.” he continues “if we as an industry choose this 2D to 3D post-production conversion, it’s the end. As quickly as it got here, that’s how fast it will go away.” Need I say more except thank you Jeffrey Katzenberg for saying everything I wanted to in such an eloquent and quotable way!

There are so many downsides I can see to 3D cinema which still make me unsure about it, apart from the laziness to actually think of a good story there’s the added expense to us as cinema goers (an extra £2.10 for a 3D film and 80p for the glasses if you need them at my cinema), the darker less vibrant image you get looking through the glasses, the cheap, uncomfortable polarising glasses you have to wear and the fact that not everyone can see the effect.

On top of that I have one final personal gripe, they put signs up (quite rightly) warning epileptics ‘this film contains flashing lights” but they don’t check people can see in 3D before paying out to see a film. In my professional capacity as an Optician I’ve had a couple of patients who have complained they thought the 3D of Avatar was rubbish, when I spoke to them about the fact they have a lazy eye (one eye doesn’t work very well) or a squint (one eye turns in/out) and so they’re eyes don’t work together so can’t perceive the 3D effect. Researching this article I found out one of the original 3D film’s director could not see in 3D, genius, how do you know it works if you can’t actually see it, it would be like a chef with no sense of taste or a composer who was deaf …… wait, hmm Beethoven – forget that analogy!

As you can see there are a lot of pitfalls and from my experience I have only seen 3D used successfully once in Avatar. The 2D to 3D conversion films I’ve seen look fake and don’t offer anything extra to the cinema experience, will 3D movies last, who knows only time will tell I guess. I hope that gives you a bit of an insight into 3D and how it works. I’d welcome anyone else s thoughts on the current 3D fascination.