The scene you're about to watch
is perhaps one of the most important
and influential sequences in the history of cinema.
Okay, this could use some explanation.
This is a scene from "Mary Poppins," a 1964 classic
directed by Robert Stevenson.
It's 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.
(gasping)
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.