Since its inception, cinema has evolved a lot, gaining sound, color and special effects. The latest news is 3D movies, which need special glasses like the ones below to watch.
In 3D movies, scenarios, people, and even cartoon characters can be viewed three-dimensionally, as if they were real and closer to us. So the idea of their producers is to "fool" our brain and our eyes into thinking that they are in front of a three-dimensional space and not in front of a common two-dimensional screen.
To understand the workings of 3D cinemas, it is crucial that we know that humans have binocular vision, so that each eye sees a different image, and the brain is responsible for combining them into a single image.
The (almost imperceptible) angular difference between these two images, called Detour, is used by the brain to aid in depth perception. It is precisely for this reason that, by losing sight of one eye, people also lose the spatial notion.
Old 3D movie productions used images anaglyphs to take advantage of binocular vision and deviation. These images include two layers of color on a single strip of film reproduced by a projector, one of which is red and the other blue (or green).
So when we wanted to watch these movies, it was necessary to use a 3D glasses with one red and one blue (or green) lens, like the ones at the top of this page. These lenses "forced" one eye to see the red section of the image and the other the blue (or green) section.
It is because of the differences between the two lenses that the brain interprets them as a three-dimensional image. However, because of the use of color lenses, the "final image" staining is not accurate, so there is data reporting that this technology has brought many problems for people such as headaches, eye injuries and nausea.
For this reason, another technique became more widely used, which is the polarized. Although it is more expensive and complex, it is more faithful and retains the original colors. Each image is projected with a different polarity (sometimes with two simultaneous projectors). In this technique, glasses with special lenses are also required for viewing. Each eyeglass lens has a different polarization filter: one lens filters the polarized waves vertically and the other horizontally. As the polarized lens slightly darkens the images, the projection screen is silvered to increase the brightness of the image.