3D movies have been around since the 1950s, but in the last decade they have become  more popular than ever. This type of movie is filmed differently and in a way that brings out a third dimension, which imitates human vision. This technique helps create a depth effect, which is close to what our eyes see in our everyday life.
To fully understand how 3D technology works, we must first understand how our eyes are able to see in three dimensions. 3D vision is also called stereoscopic vision. In order to create a depth effect, each eye records a different image. To notice the difference, let’s do a little test! Hold a finger in front of your face, then close an eye. Then open the other eye, closing the first simultaneously. You will find that your finger has moved, because the right eye records an image that does not have the same angle as the left eye. The brain then deals with combining the two images to give an impression of depth. Due to  this, we are able to estimate distances. Thus, a person who can only see from one eye cannot perceive the 3rd dimension, and will not be able to watch a movie in 3D either.
To produce a three-dimensional film, you have to provide each eye with two different images, which is possible thanks to special glasses that separate the images of the right eye from those of the left eye. During the shooting of the movie, a camera equipped with two lenses is used, in order to record an image for each eye. The gap between the two lenses is usually similar to the one between the two eyes, to reproduce stereoscopic vision. Two different cameras can also be used. These methods allow you to capture images from two different angles, just like our eyes. Significant work must then be done in post-production to give the effect of depth.
If we watch a 3D movie without glasses, the images will be superimposed and blurred. To separate them, you have to watch the film with 3D glasses, which isolate the images of the left eye and the right eye. Currently, the most used technology in the field of cinema is the polarization filter. Do you own polarized sunglasses? They block the light in the horizontal direction, to reduce glare. The same principle applies for 3D glasses. A filter separates the light into horizontal waves for one eye, and vertical waves for the other. This allows for the separation of the two images. The polarization thus makes it possible to prevent the right eye from seeing the image on the left, and vice versa. In the end, the brain assembles the images to produce a perspective effect.
3D glasses can be restrictive for some people, especially those who wear glasses. However, it is impossible to see a film in 3-dimension without wearing them. At the present time, current technologies do not allow us to watch 3D movies at the movie theatre without glasses. Who knows? Maybe one day we will be able to see a film in 3-dimension without wearing them!