How Things Work: 3-D movies

Watching a movie where a sword comes right out of the screen at you can be a thrilling experience. Filmmakers make this possible by using 3-D technology that makes the audience feel as if it is part of the action. As stated in an article on, the first 3-D film, The Power of Love, was released in 1922. Since then, the technology has been used by filmmakers far and wide.
In order to experience the 3-D effect, one has to wear specially designed 3-D glasses. The 3-D effect is possible due the phenomenon of binocular vision, because of which humans see the world in 3-D. Humans see their everyday world in three dimensions because of the interaction between the images received from both of their eyes. The effects of binocular vision can be explained by considering a simple fact — the accuracy at recognizing things changes if the world is viewed with one eye closed.

As explained in the Encyclopedia of Virtual Environments, developed by members of the Human Interface Technology Lab (HITLab) in the University of Washington, binocular vision occurs because our eyes are spaced approximately 2 inches apart. With a gap of 2 inches between them, the two eyes view the world differently. The brain is able to correlate both the images and put them together to make the world appear three-dimensional. Since images of far-away objects tend to be unclear due to poor resolution and blurring, it is hard for the brain to recognize such an image. If only one image reaches the brain, this recognition process is even more difficult. Thus, with one eye, it is harder to realize the proportions of the image because the image from the other eye is missing.

After analyzing the mechanics of binocular vision, which allows humans to distinguish between the 2-D film screen and theater performances, scientists were able to come up with a method that allowed the movie-goer to see the action of a movie in 3-D. They made this possible by devising a technology in which a person in the audience simultaneously sees a different image with each eye. The two images are then put together by the brain. So even while sitting in the theater, one can feel as though he or she is sky-diving or stepping on the surface of the moon. As stated in the article “How are 3D films made” available on, a 3-D film is able to make us view two different images because it is shot separately using a special camera that records it onto two different filmstrips. These shots correlate in the same way as images received by each of our eyes would if the eyes were in the place of the camera. When the film is played, the shots are projected onto the screen on top of each other. The 3-D glasses allow us to distinguish between the images, because with the glasses on, our left eyes see the shot projected only through the left projector and the right eyes sees the shot projected by the right projector. Our brain mixes the images together and gives us the 3-D effect.

Traditionally, this was made possible by the use of different colors in the same shot. One image displayed on the screen was in red, the other on top of it was in either green or blue. The glasses were made in such a way that one lens could only filter the red light and the other could only filter the green/blue light. Two different images reached the eyes and the brain did the rest of the job. While colors were being used as part of the technique for separation, the drawback of this technique was that one could not really watch a colored 3-D movie.

Polarized 3-D glasses use the technique of stereoscopy to give a 3-D illusion. These glasses are based on the principle of polarization of light. Polarized light oscillates in only one plane, and different polarization filters cause the light waves to oscillate in different planes. A film using stereoscopy consists of two images projected simultaneously on the same area of the screen through polarizing filters that are oriented at right angles to each other. Thus, each image consists of light that oscillates in a different plane. The polarized 3-D glasses have similar filters. Therefore, light through one filter passes through it only if the light itself is similarly polarized. Hence, the key to 3-D vision is achieved again — two different images reaching the two eyes simultaneously. Some wonder why a 3-D film viewed without glasses appears to be a strange sight that is very fuzzy and out of focus.

The reason for this is the use of two different images, which are not registered by both the eyes as different if 3-D glasses are not used.
The world of 3-D makes a person reach out to places like the solar system or underwater while sitting in a neighborhood movie theater. A simple scientific concept has thus been used to help audiences have completely new experiences.