More and more movies are being offered in 3D in theaters, so almost all of us have experienced this new cinematic technology. But do we all know how 3D movies work in theaters? The ingenius technology works by exploiting human spatial vision (discussed previously in episode one.This involves some special equipment: a special projector, 3D glasses for viewers and a specially coated screen.
A movie that is intended to be shown in a 3D format in the theater must also be recorded with a special camera. This camera features two lenses and always records two perspectives of the scene during filming, and these are placed together during the editing process. These two perspectives are the basis of digital 3D technology and how it uses the human brain to produce surreal effects.
Special glasses for 3D vision
In order to be able to utilize three-dimensional vision in theaters, the recorded perspectives must be assigned to the individual eyes. The easiest way to achieve this is to use special glasses. In this case, two types of glasses have been developed: polarization filters and shutter glasses.
The polarized filter glasses technique (provided by: RealD) only allows light waves of a certain polarization direction through the lenses; each lens allows the opposite polarization direction. The 3D projector offsets the images for the left and right eyes in the various directions. Projection of the film occurs on a canvas coated with silver, which is then reflected back so that the polarized beams are perceptible to the audience. Polarized filter glasses ensure that only the correct images fall on the corresponding eye, since these are only able to pass through the right or left lens. The brain combines this information and enables us to perceive the intended 3D images.
3D via shutter technology
Shutter-style glasses (provided by XpanD) perform the same function, however the technical aspect is somewhat different. The lenses of the glasses use liquid crystals (just like in an LCD TV) that control the light that is able to pass through the lenses electronically by opening and closing them. The film is played at a frequency rate of 60 images per second. The shutter glasses open and close the left or right lens 60 times per second. They are controlled by infrared to ensure that each separate eye is able to see only every other image in alternation. Remember, people perceive movement in a film as fluid when they are shown at 24 images per second. Since the number of images is separated, the images are shown at a high frequency. At 60 images per second, each eye sees 30 images, which results in fluid movement. This allows the brain to “calculate” the 3D effect.
Which 3D technology is better?
Most moviegoers prefer the shutter technique in terms of visual quality. Since the image does not need to be polarized, it doesn’t lose any color or focus. The disadvantage is that these glasses are relatively expensive and heavy. The polarization filter technique, on the other hand, provides a good, low-priced alternative to this. Even if the image quality may not be the best possible, polarized filter glasses are very light and comfortable to wear. They aren’t as costly and financial damages can be kept at a minimum in case they are lost or destroyed.
The decision about which technique for presenting 3D is used at your favorite theater rests with the theater’s owner. It remains to be seen whether 3D technology will become so popular that all theaters will need to install the equipment. Several of Hollywood’s big names, including Christopher Nolan (“Inception”), want to wait until 3D technology has developed more before they produce their movies in this style.
(Translated from Andreas Ruddat’s German Original)