3D movies: The science behind the magic

Published: February 4, 2011
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Cinemas used to project a red and a blue image along with the normal colored movie

The first step to understanding 3D films is understanding how our mind perceives 3D, or to put it simply ‘depth’. Each of our eyes sees a slightly different image and the brain puts these together to form a 3D image.

If you close one eye you are technically seeing 2D however, your brain assumes so many things that it doesn’t make much of a difference. But if you hold up something close to your face and then look at it with one eye in turn you will notice a huge difference in the image.

So this is simple.

All that needs to be done is to fool the brain into thinking that it is getting two images and let it put them together to form a 3D image.

Animated 3D movies are made normally but when they render them they make two movies from two different carefully placed cameras that represent each of the viewers’ eyes. When shown in cinemas both the recorded movies are projected onto a special screen using two projectors.

The projectors project perpendicularly polarized light with respect to each other and the screen maintains this polarisation. All that is needed are simple 3D glasses with polarised frames that make sure that the image made from the right camera coming from the right projector goes into our right eye and the light from the left projector goes into the left eye and our brain puts it all together to give us stereoscopic 3D vision of a 2D screen!

Earlier cinemas used to project a red and a blue image along with the normal colored movie that that were adjusted to go into the left and right eye by the help of glasses made of red and blue transparent films that acted like filters. These 3D movies could be projected in any cinema as the light did not need to be polarized.

Cinemas in Pakistan have featured 3D movies like ‘Spy Kids in 3D’ and others with the help of the older technology. The recently launched the Atrium cinema in Karachi however hosts the newer polarising projectors and offers a 3D viewing experience not seen before in Pakistan.

Magic, no. Physics, yes!

hassan.bukhari

Hassan Bukhari

A bachelors student majoring in physics at the LUMS School of Science and Engineering. He blogs at The Box Move.

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