For the optics nerds out there:
The upcoming release of Avatar got me researching the competing 3D technologies currently in use to project 3D films. I was so impressed with the quality and color of Coraline, and now I see why – this stuff’s advanced! Come and follow me on a guided tour through Wikipedia…
The oldest and most robust 3D images were created using two different colors – red and blue, for example. With red- and blue-filtered 3D glasses, a different image could be sent to each eye. This was adapted to color images with very minimal success, and just isn’t a very beautiful way to watch movies.
The next leap involved using polarized light. A polarizing filter takes a standard light wave, which is oscillating at all angles as it travels to the eye, and filters it so it is either horizontal or vertical. A longer explanation can be found here. This technique is susceptible to all sorts of odd effects if the viewer’s head tilts to one side.
Now there are two systems: RealD Cinema, and Dolby 3D made by Dolby, who seems to remain in the business of patenting awesomeness. RealD circularly polarizes the light, which I didn’t know was even possible and is a very robust means of projection. The downside of the method is that it requires a special silver screen to display images; the upside is its glasses are very cheap.
Dolby 3D’s approach appears to be even more sophisticated. It splits the spectrum to yield two slightly off-color blues, two slightly off-color reds, and two slightly off-color greens. Through very sophisticated ($50!) glasses, it sends each of those colors to different eyes.
The battle between these different projection technologies and the difficulties in adopting 3D altogether are well-explained by David Bordwell in a recent post.