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Lights, Camera... Polarise

Movies can offer a much-needed escape from our own reality. In the last decade, the movie industry has upped the ante when it comes to creating an unforgettable, engaging adventure through 3-dimensional (3D) motion pictures. This week we take a look at the science behind 3D filmmaking that is largely based on the human visual system.

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First, let's take a detour and get to grips on how a photograph is captured. The electromagnetic spectrum is a range of frequencies and wavelengths of radiation and only a small portion of it is visible light to the human eye. This portion includes the range of colours we see, classified broadly into red, green and blue (RGB) channels. Objects only appear coloured because they reflect the different wavelengths of visible light. Cameras are designed to freeze a moment in time by capturing this reflection of colours. This reflected light inside the camera activates a chemical reaction to 'trap' this moment onto the photographic film when the shutter clicks. And there you have it! A visible memory to last generations. Historically, a movie was simply a sequence of transparent pictures aligned on a long strip of film. The more pictures within a frame rate (in seconds), the more continuous the movement looked, however, if fewer pictures are presented in the sequence then the movement starts to look choppy. These images are projected onto the screen which reflects this light onto the back of the eye. Nowadays, films are captured digitally which has not only increased the video quality but has reduced the chances of damaging or losing parts of film strips.

Then what is so interesting about 3D films? In short... everything!

3D movies mimic the natural form of vision humans use to navigate the world: stereoscopic vision. This process extracts information (contrast, luminosity, the distance between objects and object contours) from 2-dimensional representations to help us perceive an important visual cue: depth [1]. This cue informs us where in 3D space objects are, how quickly and in what direction they are moving to then notify us on what the appropriate response is to engage with it. Because your eyes give two slightly different perspectives of the same visual scene, your brain matches the two views into one image. This explains why you duck very quickly when something unexpected is thrown at you.

The 3D Experience!

How exactly are 3D movies filmed? They use a special camera that has two separate lenses to capture the same scene from two slightly different perspectives. In this way, the camera records two perspectives which are edited together (mimicking the way our brains would combine two images) to give the perception of an image moving out of the screen towards us. This creates a more 'surreal' viewing experience.

To merge these two images into one, each perspective needs to be assigned to each eye using special glasses. Cue the funky blue and red glasses. These glasses act as a polarised filter to guarantee that only eye-specific images are directed to the correlating eye. The glasses convince the brain that the two images directed are from different positions which trigger that useful depth perception cue we spoke about.

Not every individual can experience the magic of 3D cinema due to a condition called 'stereoblindness'. In such cases, the brain is reliant on information obtained from one eye as it incapable of merging separate points of space. On the bright side, people with stereoblindness can still rely on the fantastic storytelling of screenwriters and the excellence of acting, to still bear witness to a deeply moving experience with the onscreen world of films.

The 3D film medium is a very cool technical trick used to elevate the atmosphere and quality of a movie. From heartbreaking moments to the action-packed fight scenes, movies evoke emotion. Emotions that are only made that much more real during the 3D experience; giving us the most enchanting escape into a world beyond our own.

Leave a comment down below and tell us which you prefer: traditional cinema or the 3D movie experience?

[1] Mendiburu, B. (2012). 3D movie making: stereoscopic digital cinema from script to screen. CRC Press.

By Tulela Pea, Editor

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