3D is back in our cinemas and it\u2019s big business. Cinemas can charge more for 3D movies, 3D movies earn more revenue and \u2013 along with monster screens \u2013 are another key differentiator for cinema, in this frighteningly modern age of Blu-ray, iTunes and Bittorrent (whatever that is).<\/p>\n
Of course, 3D is nothing new, and I don\u2019t want to use this space to reproduce Wikipedia entries about its history, nor whine about it being used badly or inappropriately, nor even do I want to assess its place as another colour for moving picture artists to add to their palette. I want to talk about something more fundamental \u2013 what is it?<\/p>\n
The briefest of history lessons, just to explain why 3D is suddenly back in our cinemas, and to add a little context. 3D in this sense essentially means delivering two subtly different images to each eye. This can be done in various ways, with the most popular in the twentieth century being the red\/blue anaglyph method. This sends a red-tinted image to one eye and a blue-tinted image to the other eye thanks to cardboard glasses. The method is cheap to implement but entails obvious compromise of colour within the images. LCD shutter glasses which blocked all light reaching each eye alternately were briefly experimented with but you can\u2019t give out expensive items of electronic equipment free with breakfast cereal and they need both power and careful synchronisation with the projected image. Neither is ideal, which is why 3D was so niche for so long.<\/p>\n
The reason for the current swathe of 3D movie is that two new technologies have caught up with an existing one. The glasses you get given at your local Vue or Odeon today are polarised, which effectively means that half the light enters one eye and the other half enters the other eye. No colour distortion, but a dimmer image, and you can\u2019t just blast twice the light through 35mm film to make up for the shortfall, since twice the light means twice the heat and you\u2019ll melt the celluloid. However, the advent of digital (filmless) projectors combined with hugely reflective metal screens means that polarisation can be deployed without the images being reduced to a murky gloom. Reflective screens + polarised glasses + digital projection systems = $$$ it seems.<\/p>\n
And more is to come \u2013 3D TV is on its way, with several lenticular (you know, like those corrugated postcards which seemed to move if you tilted them) systems which send a different image to each eye, provided you sit in just the right position and keep your head still.<\/p>\n
But what exactly is the benefit of all of this?<\/p>\n
Well, it isn\u2019t 3D except in the very trivial sense that the images you are watching now have an apparent third dimension of depth to add to their existing dimensions of height and width. No, it\u2019s stereoscopy or stereo imagery which is no more like actually being there than a stereo recording is actually like being at a concert.<\/p>\n
Let\u2019s start by considering how our brains interpret the three-dimensionality of the world at the moment. Information about how near or far things are comes from three sources.<\/p>\n
Of these three, perspective is present in any photograph of the world, and is obviously a part of any movie, 3D or not. The second, parallax, in the first sense is equally present in any live-action movie and, was a key reason for Walt Disney to create his multiplane camera<\/a> in the 1930s. However, in the second sense, it is absent from all movies, 3D or not. You can\u2019t move your head and see a different image as you could if you were witnessing the events live. The 3D stereoscopy is an illusion, one which is shattered if you try and interact with the image in even the most trivial way. We are not Luke Skywalker, able to walk around the projection of Princess Leia and see her from whatever angle we please. At least with your “RealD” glasses you can move your head without the image actually falling apart, unlike those lenticular TVs I mentioned earlier (disclaimer: this technology will obviously improve over time and I haven’t sat in front of one myself yet, so I know not whereof I speak \u2013 but that’s the prerogative of a blogger, is it not?).<\/p>\n