Mary Poppins

Walt Disney (1964)

When Jane (Karen Dotrice) and Michael (Matthew Garber), the children of the wealthy and uptight Banks family, are faced with the prospect of a new nanny, they are pleasantly surprised by the arrival of the magical Mary Poppins (Julie Andrews). Embarking on a series of fantastical adventures with Mary and her Cockney performer friend, Bert (Dick Van Dyke), the siblings try to pass on some of their nanny’s sunny attitude to their preoccupied parents (David Tomlinson, Glynis Johns).

Mary Poppins is a film often regarded as Walt Disney’s crowning live-action achievement, being the only Disney film to ever be nominated for Best Picture in his lifetime. But there’s something else that’s often overlooked about this film. It was also that year’s winner for Best Visual Effects. Now for a film featuring a magical flying nanny, you might not find that to be surprising at all. But it’s this overlooked achievement that helped Mary Poppins change the course of film history forever.

Like all forms of art, films have always relied heavily on bringing our imaginations to life. As films evolved, this posed a great challenge for early filmmakers. Imagination had no boundaries — but film did. At the time at least. Early on, simple camera tricks were used to make the impossible look possible. George Méliès, one of the first pioneers in visual effects used a technique known as double exposure mattes to achieve this feat over a hundred years ago. A man with multiple heads. He did it by putting a glass panel in front of the camera and painting black marks over specific sections to block the light. He would then rewind the film, and set up an opposite matte to fill in these blanks individually. Then voila! Despite its many limitations, the double exposure mattes were used for many years, until something a little more familiar to us arrived on the scene.

This is the blue screen, developed by Lawrence Butler and it looks and works similar to the green screen we use today. With the arrival of color films, Butler realized he could put a subject in front of a specific color, then remove that exact color to isolate a subject from its background. The isolated subjects would then be placed on top of a pre-shot background known as a plate to create a single seamless image. This is the start of what we now commonly know as chroma key. This method was first used in 1940 for the film “Thief of Baghdad” but it also came with many issues. The color blue was selected mainly because it was a color farthest from the skin tone. But this meant that any costumes or props with a blue hue would simply blend in and disappear with the background. And if the lighting wasn’t perfect, it would end in these blue halos that you see around the actors.

So when Walt Disney acquired the live-action film rights to “Mary Poppins,” they wanted to take the opportunity to push the technology even further. Especially for one particular sequence, where live-action footage merges with Disney’s classic hand-drawn animations for over 16 minutes. But instead of hiring a special effects artist for the job, Disney instead asked for help from the engineer and inventor Petro Vlahos.

So, what did Vlahos do to begin? Well, he got rid of the blue screen. Fully aware of its limitations, he sought for another color to replace it. His answer? Yellow! Well, more specifically, the yellow hue from sodium gas. The same light you see in street lamps. Vlahos knew that sodium gas produces light at a very exact wavelength, 589 nanometers. In comparison, the blue used in blue screen ranges from 435 to 500 nanometers. By shrinking the range of wavelengths, Vlahos knew he could greatly improve the accuracy when isolating a subject. This already solved many problems from its predecessor. For one, things didn’t have to be lit as perfectly. And there were no limitations on the colors of props or costumes. For example, Dick Van Dyke could wear this blue bow tie and socks, and because sodium gas emits a very specific hue of yellow, he was also able to wear a blazer with yellow stripes. To achieve the effect, the actors would stand in front of a white screen lit by a yellow hue from sodium vapor lights, hence its name, the sodium vapor process. Unlike the blue screen, which required tampering with actual film strips to achieve the effect, Vlahos’ method was completely within the camera. He did this by creating a unique prism that was designed to isolate the 589 nanometer hue from the rest of the colors. This simplified the process of creating a more accurate matte, the silhouette image that’s vital to the process. The result was astounding. Even by today’s standards, it’s difficult to find a fault. Isolating a more specific range of wavelength allowed for a crisper image, practically eliminating the halo effect of the blue screens. You need to look no further than this veil that Julie Andrews is wearing to see how impressive this technology really was. Up until then, isolating a material as fine as a veil was deemed impossible until Vlahos’ new invention. And it was this technological marvel that earned Vlahos the Oscar for Visual Effects. There was an issue, however. Despite multiple attempts to replicate it, Vlahos could only create just one working prism which meant there was only one sodium vapor camera, in the entire world. After showing its capabilities in “Mary Poppins,” other studios and filmmakers fought to use it. And this single technique would go on to be used for almost 40 years, in notable films like Alfred Hitchcock’s “The Birds” and the original “Pete’s Dragon.”

After the success of “Mary Poppins,” Vlahos would go on to further develop and improve the chroma key process. The result was what eventually became the basis of the modern green screen. For this reason, Vlahos is often regarded as the man who made the modern blockbuster possible. Without Disney’s gamble and Vlahos’ ingenuity and innovation, we might have never seen “Mary Poppins” on the silver screen, not to mention films like “Star Wars” or “Jurassic Park.” With “Mary Poppins,” Vlahos not only gifted generations of people with one of the most beloved classics of our time, but a legacy that can make all of our wildest imaginations come true.

  • By Nathaniel Lee


  1. I’m sure a lot of the early special effects was done by trial and error, and Disney was a perfectionist. It was a good movie. Never had the pleasure of reading the books though. Perhaps that will my next endeavor.

  2. So fascinated by people like Vlahos, who obviously had a creative mind but ALSO the tech-savvy sort of scientific mind to come up with prisms that (sic) “isolated hues from other colors”.
    What is that? Using both sides of the brain equally? I like to think of myself as *creative*, but I could never, in a hundred million years, think of and/or come up with a solution like him for special effects. So I’m obviously a lopsided one-sider over here. 🙂
    But that’s okay. That movie is one of my most favorite memories ever. Read the books as a kid, too.
    It’s strange to think that not only can I say “supercalifragilisticexpialidocious,” very quickly with no problem but can probably spell it, too, with 98.% accuracy. And a lot of people can do that! I have to look up hors ‘duerve every single time to see how it’s spelled (see? spelled it wrong there too!) but supercalifragilisticexpialidocious? No brainer, lol !!!

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