[0:00] This is a scene from Stanley Kubrick's 2001: A Space Odyssey released in 1968.  This was before computers
and digital effects.   So, how do you think he made
this pen float in space?    The obvious answer is string, but this would get tangled up 
every time the pen rotated   and would ultimately be 
impossible to hide.  The real trick behind the shot was
 simple but extremely effective.   The pen was attached to a large piece 
of glass with double-sided tape
[0:29] and placed in front of the camera.    The glass was attached to bearings  that allowed an operator to slowly 
move and  rotate the glass  to mimic the floating movement.  It was incredibly simple, but the
 end result was perfect.  This is just one of many creative tricks   that allowed filmmakers to
 pull off crazy visual effects, all before computers and CGI.  They managed to duplicate heads,  make characters invisible,   turn miniatures into 
enormous movie  sets,
[0:58] and even invent a green screen alternative that worked better 
than today's digital methods.  This scene from The Man with the  
Rubber Head is over 120 years old,  and it shows filmmaker Georges Méliès inflating a copy of his own head.  But how did he pull this off in 1901?  You might think that these are 2 separate films layered on top of each other.   But that's not the case.  In fact, everything was captured in-camera  and so what came out 
was the finished film
[1:28] and it didn't require editing.  To pull this off,  he'd record the first scene 
with a black sheet   placed in the area where the 
head was going to appear.  Then he'd rewind the film back to the start and set up the second scene 
with only his head visible  against a black background.  This time he'd record directly 
over the same strip of film  used to record the first scene. Because this was being recorded 
onto a transparent film negative,  the dark areas around his head
[1:53] essentially remained transparent since almost no light was hitting the film.  This meant that as he 
recorded over the original scene,  only his head was exposed 
onto the film strip,   combining the two shots perfectly. But the real trick was how he managed to make his head grow and shrink. The obvious idea would be 
to use a zoom lens  to slowly make his head fill the frame.  But zoom lenses didn't even exist yet.  Instead, Méliès set up a ramp 
where he could sit in a cart
[2:22] and be slowly pulled towards the camera.  As he got closer, his head 
would grow from the neck until it eventually filled the entire frame.  The result was incredible 
by 1901 standards,  and this multiple exposure technique went on to be mastered in Kubrick's 2001. For these space shots,  he'd first shoot the moon on its own  with one half of the frame
being completely dark.  Then, sometimes months later,  he'd rewind the film and record the spacecraft shots directly over
[2:52] the same strip of film.  By doing it this way,  instead of combining 
separate films into one,  there was no quality loss,  and the film that came out of the camera was essentially the finished shot,    as if the moon and the spaceship 
had been filmed together.   Filming everything in-camera was another key feature of this next trick from the 1927 classic Metropolis.  These scenes placed real actors in enormous futuristic looking sets.  But not only was this all done in-camera,
[3:22] it was all done in one take without 
the need to record over the film strip.  For this shot, the actors were 
walking down a platform  far away from the camera in order
 to appear much smaller.  Then, directly in front of the camera,  they placed a mirror at 45°  which reflected a detailed miniature model of the futuristic city into the camera.  By cutting out a very precise 
portion of the mirror,   it allowed the camera to see through the mirror to the actors in the distance.
[3:50] The same trick was used for this scene.  The massive demon mouth 
wasn't massive at all.  It was actually a much smaller miniature just off to the side of the camera.  But when everything lined up perfectly,   it looked like the actors were 
walking straight into its mouth.  Just 2 years before this,   the film Ben-Hur pulled off a similar trick  of turning miniatures into massive sets,   but without the use of mirrors.
[4:15] These epic chariot racing scenes required an enormous coliseum filled with crowds but the studio didn't have the budget 
or time to build a full-scale set.   Instead, they built the bottom 
half of the set for real  and faked the rest with miniature sets hanging in front of the camera.  By placing them close to the camera,  these miniatures became 
enormous movie sets, matching the scale of the 
real set perfectly. The miniatures even had 
fake audience members
[4:43] that could be mechanically moved 
up and down to simulate a cheering crowd.  To pull all these tricks off,  the filmmakers had to make the most 
out of the tools that were available.   Nowadays, things are done very differently with digital effects and AI tools.  That's where Outskill, 
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[6:03] So far, all of the tricks we've looked at were about adding more things to a scene But what if you wanted to 
make something disappear?  That's exactly the kind of trick 
that was mastered in the 1933 film  The Invisible Man.    The main character drinks a potion 
that makes him invisible,   and he ends up going on a rampage 
while the police try to track him down. Throughout the film, multiple exposures were used 
to make the man invisible.
[6:28] But it's this shot of the man 
running through the snow  that we're going to look at.  In order to pull this off,  a fake wooden floor was created  and footprint-shaped holes 
were cut into the wood. The floor was covered in powdered snow  and one by one the wooden 
cutouts were released  causing the  snow to fall and make footprints in the ground.  This blew people away in 1933 and the invisibility effect looked incredibly realistic.
[6:55] But what about scenes that 
aren't meant to look realistic at all?   Like these scenes from Kubrick's 2001.  These shots were so abstract  that they couldn't be achieved by simply pointing the camera at something.    In order to pull it off, the visual effects supervisor had to get inventive.  He placed the camera on rails 
and pointed it towards a black screen  with a thin slit in the middle.  Behind the screen was a super 
long piece of artwork  that was backlit by bright lights.
[7:23] The camera was tilted slightly off center so that when it moved forward,  the slit would travel from the middle of 
the frame to the edge of the frame.  By keeping the shutter open 
for the whole duration of the move,   it created a streak of 
light across the frame,  just like when you take a 
long exposure image of a car at night.   As the camera moved forward,  the colorful background would 
move a few inches to the right,    revealing different parts of 
the artwork through the streak.
[7:49] This single movement 
only created one frame  and so the process had to be repeated hundreds of times to get the full sequence. To record the other half of the frame,  the camera was tilted 
in the opposite direction  and the entire process was repeated  using the multiple exposure trick to 
record directly onto the original film.   The amazing thing is this machine was completely automated and it ran constantly for several 
hours at a time to create these shots.
[8:16] But perhaps the most impressive 
of all of these techniques  is one that no longer exists,  but it was so perfect  that even the digital techniques 
today struggle to match it.  You're probably familiar 
with green screens. Put anything in front of one, 
key out the background,  and replace it with 
anything you can imagine.  This trick has been around 
since the 1940s   when it was more common
 to use a blue screen. But this whole technique had major drawbacks that still exist today.
[8:44] Actors were constantly surrounded 
by this horrible blue glow.  Any kind of motion blur would 
reveal the blue background.  Detailed parts like hair 
would lose their sharpness    and transparent objects 
simply became invisible.  The problem is that even if 
the background is perfectly blue,  the camera doesn't see it that way.  Areas close to the actor blend together  and become vastly different 
shades of blue. Even with modern digital techniques,
[9:10] it's almost impossible to avoid these problems when keying out backgrounds.  But in the 1964 film Mary Poppins,   
Disney somehow nailed this effect.   The semi-transparent veil 
blends in perfectly.  The salt leaves no trace,  and the actors are even wearing blue 
and green clothes throughout the film.  The edges are so perfect, better than  almost anything that's possible today.   So, how did they do it?  Instead of a blue or green screen,
[9:37] the actors were standing 
in front of a white screen  which was lit by powerful 
sodium vapor lights.   These lights emitted a very specific wavelength of light at 589 nanometers. And so it was very easy to 
separate only this wavelength    without affecting any other colors.    Inside the camera was a special prism with a coating that was extremely sensitive to this exact wavelength.  As the light entered the camera, the regular color light passed 
through onto a strip of film,
[10:05] but the sodium light was separated and directed onto a different strip of  black and white film.    The result was a 
black and white silhouette  that perfectly masked 
the shape of the actors.  This silhouette could be 
used as a transparency mask.  Essentially, everything that 
was white became transparent  and everything that was black 
remained in the shot. But it wasn't just black or white.  For blurry or semi-transparent areas, the silhouette mat would 
be a shade of gray
[10:32] and essentially allow some 
of the original image through. If the original footage had been 
filmed on a bright blue background,  this would simply allow part
 of that blue to leak through. But with the sodium vapor technique,   there was essentially no background at all.  The color film didn't 
detect the sodium light, and so almost no light from the background would end up on the film strip.  When it came to those 
semi-transparent areas, there was no light beneath 
the mat to shine through,
[10:59] creating perfect transparency.  By the 80s,   this technique was largely forgotten about  since it was almost impossible
 to replicate the prism.   Nowadays, digital effects 
have taken over the film industry, but it shows just how much creativity 
went into the magic of these old movies.   Thanks for watching, 
and I'll see you in the next video.