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.
