Ways to see 3D

In the chapter How 3D Works we learnt that 3D vision and the perception of depth is one of the consequences of having two eyes and brain’s wonderful capacity to create 3D image from two slightly different images of the same object.

So how is that 3D reality we live in recreated in 3D movies and games?

Every 3D technology relies on the stereopsis – the ability of the brain to create a 3D image upon left and right image from the eyes. So every 3D technology is trying to make left eye see the image it is supposed to see at the same time (or nearly the same time) as the right eye sees the right image.

The most effective 3D method before digital age was anaglyph method. The finished movies (left and right one) were processed with different colour filters (blue and red or green and red) and merged into a single movie. The paper glasses with red and blue foil for each eye then blocked out the images for each eye, so the 3D effect was created.

This method was very effective with black and white movies, but as the movie industry moved into colour it turned out that the method had many drawbacks: two projectors were needed, the synchronization of them was a big problem and the resulting colour of the movies was problematic to say the least. Anaglyph method with red and blue eyeglasses lenses is considered a history – at least for cinema and consumer electronic world, although there are other systems that use the same idea of colour separation even nowadays.

Digital projectors are usually capable of projecting the stereo images in a frame-rate that is high enough to recreate the 3D effect with single projector setting.

The term polarization based passive systems nowadays usually applies to systems that use different polarization to separate the stereo images (although there are other types of passive 3D systems). At the projector either electro-optical modulator or rotating filter wheel is used, where filters have different polarization characteristics. To make sure the correct image reaches the correct eye, viewer wears glasses where each glasses lens has different polarization.

There are many disadvantages to passive system: polarization of the light can only be preserved with the silver screen (in case of cinema exhibitors this means a big investment and inability to move a 3D system to other hall in a multiplex), passive systems have significant problems with ghosting (“objects” in a movie having a ghosty shadow) and usually they require dual projector system to prevent the loss and uneven distribution of light.

Read more about the active shutter 3D technology in the chapter XPAND Active Shutter 3D.

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