Have you ever wondered how 3D films work? The truth is, they aren’t really three-dimensional at all. If you were to walk up to the cinema screen, you would find it as flat as it ever was. So, how does it work? It’s all a trick, really. Your brain is fooled into seeing two different two-dimensional pictures as one three-dimensional image. And this is exactly what your eyes and brain do in the real three-dimensional world, all thanks to something called stereoscopic vision.
When you stand still and look at a stationary object near you, your brain combines the two images from each eye as one. But it’s also using the differences between the two images to work out how far away the object is. This is what’s known as depth perception, and it’s why we have two eyes and not just one. If you cover one eye, you’ll find it much harder to play something like table tennis.
So, how do 3D films achieve this effect? By delivering a different image to each eye. The old-fashioned way of filtering what each eye sees is with those silly cardboard spectacles with one red lens and one blue lens. The red lens only lets red light through, and the blue lens only lets blue light through. The film contains red and blue images of the same scene, but shot through two different lenses. This is exactly how your eyes work. And then, your brain performs its usual trick of reassembling the picture with depth. However, the colors are pretty horrible, and one arm of the glasses usually breaks off.
A more sophisticated version of the same system uses polarized light instead of colors. Polarized light has orientation, so glasses with two different polarizing lenses can divide up the picture as before. An even more sophisticated version uses something called an active shutter system. The glasses now block the eyes alternately while alternate frames in the film are received by the unblocked eye. As long as the frames change quickly enough, your brain doesn’t notice that this is happening. This is because of something called persistence of vision, where an image remains in your brain for a fraction of a second, even after it’s gone. However, the glasses are quite complicated.
Interestingly, 3D films have been the next big thing in cinema several times throughout history, usually when cinemas have felt under threat. For example, in the 1950s with the rise of television, in the 1980s with the development of videotape, and in the 2000s as home cinema and downloadable films became affordable. The first 3D film was shown in New York in 1915, but nobody was very bothered then either.
In conclusion, 3D films are a fascinating application of stereoscopic vision. By tricking our brains into combining two different images, we can experience a sense of depth where there is none. It’s a testament to the power of our brains and the ingenuity of science and technology.