Speaker 1: Welcome to tex Stuff, a production from I Heart Radio.
Speaker 1: Hey there, and welcome to tech Stuff. I am your host,
Speaker 1: Jonathan Strickland. I'm an executive producer at I Heart Radio
Speaker 1: and I love all things tech. And today's topic goes
Speaker 1: by many names like chroma key, or blue screen or
Speaker 1: green screen. The inventor of this technology developed it for film,
Speaker 1: and that pun was an intentional you know, developed for film,
Speaker 1: But I'm gonna I'm gonna run with it. Today we
Speaker 1: use this technology and film in television, on Twitch streams
Speaker 1: and zoom calls, I mean all over the place. And
Speaker 1: in the old days, you weren't likely to encounter a
Speaker 1: green screen unless you were inside a movie studio, like
Speaker 1: inside a sound stage. But today there are a lot
Speaker 1: of folks who have a green screen just stashed in
Speaker 1: their home office. So today I want to cover this technology,
Speaker 1: it's history and development and how it works. Now, before
Speaker 1: I get into the history, which, as I'm sure most
Speaker 1: of you know, is my moodus up a ran dai,
Speaker 1: let's give a quick overview of what this technology actually does.
Speaker 1: So basically, it's a system that allows a creator to
Speaker 1: insert images, typically a background. That's your standard use of
Speaker 1: this and you do it into a shot that otherwise
Speaker 1: isn't actually in that location, so it could be a
Speaker 1: static image, or the new image might be in motion itself,
Speaker 1: so it might be video or film. This technology allows
Speaker 1: creators to shoot in locations they might otherwise have trouble
Speaker 1: getting to, like the bottom of the ocean, or in
Speaker 1: outer space, or in my old college dorm room because
Speaker 1: I was notorious for locking myself out. So when you
Speaker 1: do it well, it really enhances us scene. But when
Speaker 1: done poorly, it's incredibly distracting because it's so obvious that
Speaker 1: the people or you know whatever that are in the
Speaker 1: foreground of the shot aren't actually in whatever the environment is.
Speaker 1: But that's the basic idea. It's to create a composite,
Speaker 1: a combination of multiple shots into a single new shot,
Speaker 1: so that the components from those two separate shots are
Speaker 1: combined as if they're in the same place at the
Speaker 1: same time. That's the basic idea. Now let's get to
Speaker 1: the history, you know, the part that everyone really came
Speaker 1: here for. But before we even get into the development
Speaker 1: of it, we need to think about the early days
Speaker 1: of film and talk about what film really is, because
Speaker 1: that's going to help us understand the evolution of the
Speaker 1: art form that made chroma key even a possibility. When
Speaker 1: I say film in this case, I'm specifically referencing images
Speaker 1: shot on a long strip of plastic upon which there
Speaker 1: is a coding of light sensitive chemicals. Actually, there are
Speaker 1: several layers of light sensitive particles in that thin strip
Speaker 1: of film. You know, with modern film, you might be
Speaker 1: talking about twenty or more layers on that thin little
Speaker 1: piece of plastic. These layers include binding agents, you know,
Speaker 1: essentially gelatin, and grains of silver halide crystals which react
Speaker 1: to the light. These are those photosensitive chemicals, and also
Speaker 1: some special molecules that bind with silver halide crystal so
Speaker 1: that they transfer energy from specific wavelengths of light, which
Speaker 1: we perceive as different colors. When light hits the silver
Speaker 1: halide crystals coding this plastic, there is a chemical reaction,
Speaker 1: and you can think of it as a chemical record
Speaker 1: of that instant of time. Whatever light hit the film
Speaker 1: is recorded there on this piece of plastics. So if
Speaker 1: you position the lenses so that you can direct specific
Speaker 1: light to that film, you can take a photograph. You
Speaker 1: must use some form of shutter to block out the
Speaker 1: light until you're ready to take your image. Then you
Speaker 1: open the shutter. This exposes that piece of film to
Speaker 1: the light that's being reflected off of whatever it is
Speaker 1: your photographing. Remember when we see things, we're seeing light
Speaker 1: bouncing off of that and the color of the stuff
Speaker 1: we see is dependent upon which frequencies of light bounce
Speaker 1: off of that thing. So then the shutter closes on
Speaker 1: your camera and you've got your chemical record. And the
Speaker 1: shutter is necessary because, as I said, these chemicals react
Speaker 1: to light. If you just had this stuff exposed to
Speaker 1: light all the time, it would have already reacted. You
Speaker 1: would not be able to use it to take a
Speaker 1: photograph of anything. If you want to learn more about
Speaker 1: this process, which is fascinating, but really the process of
Speaker 1: photography is far enough out of the scope of this
Speaker 1: episode that I don't want to go into it much further.
Speaker 1: I do recommend you go to how Stuff Works dot Calm.
Speaker 1: That's my old employer. I don't technically work for How
Speaker 1: Stuff Works anymore, but you can go to that website
Speaker 1: and you look at the article how Photographic Film Works.
Speaker 1: It was written by Chuck Woodworth and it's a great
Speaker 1: example of the health Stuff Work style, and it goes
Speaker 1: into the chemistry and physics of the photographic process, but
Speaker 1: we'll skim over the rest of that for the purposes
Speaker 1: of this episode. So, now the film on the camera
Speaker 1: has a latent image on it, and it represents the
Speaker 1: moment in time the shutter allowed light to pass from
Speaker 1: the lens to hit the film. But in a film
Speaker 1: camera a cinema camera, you're talking about a series of
Speaker 1: latent images. Motors pull this strip of film at a
Speaker 1: steady speed through the frame of the camera where the
Speaker 1: shutter opens and closes at a regular uh frequency. And
Speaker 1: the standard speed of capturing images is twenty four frames
Speaker 1: per second, so a film camera is capturing twenty four
Speaker 1: photographs every second. The latent images needs some processing in
Speaker 1: order to create something that can be fed through a
Speaker 1: film projector. The development process creates a negative image of
Speaker 1: the chemical record, and that means that the darkest areas
Speaker 1: of the image represent the spots where the film received
Speaker 1: the most light. It's the opposite of what you would expect,
Speaker 1: right Anything that would be dark in a photograph will
Speaker 1: be light on a negative and vice versa. This negative
Speaker 1: has to be transferred onto another roll of film to
Speaker 1: create a positive image. In a process that I'm also
Speaker 1: not going to cover because we need some time for
Speaker 1: actual topic. Right. So, when we watch a film, we
Speaker 1: have the perception that what we're viewing are moving objects
Speaker 1: up on a screen, but that is an illusion. What
Speaker 1: we're really seeing with true film is that it's a
Speaker 1: series of photographs. The projector is playing those photographs at
Speaker 1: the same speed that the film camera used to make
Speaker 1: them twenty four frames per second usually. I mean, if
Speaker 1: you wanted to play stuff in slow motion, then you
Speaker 1: would shoot a film at a much higher frame rate,
Speaker 1: like forty eight frames per second, but you would play
Speaker 1: it back at the standard twenty four frames per second,
Speaker 1: and that would give you the slow motion effect. And
Speaker 1: back in the old days, cameras were hand cranked, so
Speaker 1: you would get kind of twenty four frames per second,
Speaker 1: but this would result in sort of that herky jerky
Speaker 1: movement we associate with old movies that was hand cranked cinematography,
Speaker 1: and sometimes people would turn the crank a little faster
Speaker 1: or a little slower than others, so you don't really
Speaker 1: have a consistent experience there, because the playback speed, especially
Speaker 1: if you're playing it in a modern projector, is going
Speaker 1: to be standard, even if the recording speed wasn't. But
Speaker 1: never mind all that. If you were to stop the
Speaker 1: projectors reels at any given moment in the playback of
Speaker 1: a film, you would see a still m page. You
Speaker 1: would advance the reel by one frame, and you would
Speaker 1: see the next image in the next photograph in that series,
Speaker 1: and you would likely be able to pick out how
Speaker 1: things are slightly different from the first frame you looked
Speaker 1: at and the next frame. And this is the same
Speaker 1: principle that's behind animation. If you've ever taken a pad
Speaker 1: of sticky notes and you drawn little figures on page
Speaker 1: after page after page, so that when you flip the
Speaker 1: pages you get a simple little cartoon, then you've engaged
Speaker 1: in the same art form as great cinematographers. Then maybe
Speaker 1: your work was even better than theirs. I'm not one
Speaker 1: to judge. Now, why would I go to the trouble
Speaker 1: to cover the basics of film, Well, it's because the
Speaker 1: very nature of film inspired certain people to experiment with it,
Speaker 1: to try stuff that would be impossible to replicate in
Speaker 1: a real world setting, or at least it would be
Speaker 1: really difficult. Film wasn't a substitution for theater in theater,
Speaker 1: you can create a few interesting effects. Generally your options
Speaker 1: are limited to things like lighting tricks. Maybe some creative
Speaker 1: sets are called costumes, maybe an even a stage illusion
Speaker 1: or two, and perhaps some sound design. But with film
Speaker 1: there were other possibilities, and one fellow who recognized those
Speaker 1: possibilities was the French filmmaker and illusionist George Meillier. He
Speaker 1: was born in Paris. You know Paris in eighteen sixty one.
Speaker 1: Let that sink in for a moment. This man was
Speaker 1: born while the Civil War was going on in the
Speaker 1: United States. He became interested in stagecraft and magic, and
Speaker 1: by the eighteen nineties he was a successful stage magician.
Speaker 1: In eight he saw an early film exhibition made by
Speaker 1: the Lumier Brothers and he became entranced by this new medium.
Speaker 1: His experience and illusions encouraged him to find ways to
Speaker 1: experiment with film to achieve new effects, stuff that wouldn't
Speaker 1: be possible to do in the real world. He was
Speaker 1: a special effects and film pioneer. He established methods to
Speaker 1: shoot slow motion, stop motion animation, to dissolves, and tricks
Speaker 1: like super imposition and double exposure around. Maillier had a
Speaker 1: really cool idea. He wanted to create a truly bizarre
Speaker 1: special effect in which an actor would appear to remove
Speaker 1: his own head on screen. But how would he accomplish this, Well,
Speaker 1: the secret was in shooting multiple exposures of the same
Speaker 1: reel of film. Typically, after you expose film to light,
Speaker 1: you want to avoid doing that again because you will
Speaker 1: interfere with that chemical record. You know, if you were
Speaker 1: to ever take photographs with a film camera and then
Speaker 1: someone were to open up the back of the camera
Speaker 1: and expose the film to regular light, you could potentially
Speaker 1: ruin shots that were already made, plus ruin the film
Speaker 1: for the next couple of shots. It's not something that
Speaker 1: you typically want to do. More light will cause further
Speaker 1: reactions chemical reactions on the actual plastic film, and your
Speaker 1: shot gets ruined. If you've ever used the cameras that
Speaker 1: quite line up the film properly at the very beginning
Speaker 1: of the very end, you might even notice that a
Speaker 1: couple of photos on those sections of the film role
Speaker 1: have two sets of images superimposed on top of one another,
Speaker 1: and that's because that little section of film was exposed
Speaker 1: more than once. Mellier did this on purpose. He would
Speaker 1: set up a shot and he would use a lens
Speaker 1: that had some of the lens blacked out so that
Speaker 1: light could not pass through that part of the lens.
Speaker 1: And we refer to this as a MAT M A
Speaker 1: T T E. And you can think of it like
Speaker 1: a mask for the lens, and that would mean a
Speaker 1: section of each frame corresponding to that part of the
Speaker 1: mat would remain unexposed to light. He would shoot the
Speaker 1: scene as rehearsed. Afterward, he would rewind the exposed film
Speaker 1: in the camera, beat it right back in as if
Speaker 1: he was going to shoot something all for the first time.
Speaker 1: And he would then replace this mat with a new one,
Speaker 1: and the new man at would block out everything except
Speaker 1: the section that previously was unexposed, So, in other words,
Speaker 1: the part that was black would now be clear and
Speaker 1: the rest of the lens that was previously unblacked would
Speaker 1: be blacked. So you replace one mat with a different one,
Speaker 1: so he would then be able to film something totally
Speaker 1: new into this same role of film, and this time
Speaker 1: the camera would pick up a new scene, and by
Speaker 1: changing things between one section and the other, he could
Speaker 1: create weird effects like the head removal trick. It would
Speaker 1: appear as though all of this was shot at the
Speaker 1: same time on the same role of film, but in fact,
Speaker 1: through careful control of where the light would go, Millier
Speaker 1: would use the same film twice or more to produce
Speaker 1: cool results. And if you want to see an example
Speaker 1: of what I'm talking about, and I highly recommend you
Speaker 1: check this out because it is amazing even today, go
Speaker 1: to YouTube and do a search for the short film
Speaker 1: four Heads are better than One. The activity of this film,
Speaker 1: which by the way, lasts less than a minute, is
Speaker 1: still astonishing. To say his experimental work was influential would
Speaker 1: be a gross understatement. Other filmmakers inspired by the work
Speaker 1: of Mailier tried new techniques that built upon the foundation
Speaker 1: he established. For example, filmmaker and documentary and Norman Down
Speaker 1: wanted to shoot films at historic buildings around California, but
Speaker 1: several of those buildings had been damaged or even partly destroyed.
Speaker 1: Other historic buildings had modern stuff like light poles in
Speaker 1: front of them. He didn't want that to be in
Speaker 1: the shot, so he wanted to show the buildings as
Speaker 1: they had appeared in their original form before the decay,
Speaker 1: before modern technology had advanced into the area. So he
Speaker 1: came up with a really clever idea. Dawn placed a
Speaker 1: pain of glass between the camera and the scene he
Speaker 1: wanted to shoot, and on that pain of ass he
Speaker 1: had paintings to enhance the scene. If a building's roof
Speaker 1: had caved in, he would frame up the shot and
Speaker 1: then have an artist paint a roof on the glass
Speaker 1: so that when viewed through the camera, the painting and
Speaker 1: the building behind it would line up and the building
Speaker 1: would appear to be whole again. Or he might want
Speaker 1: to cover up stuff like those telephone poles, he would
Speaker 1: have an artist paint trees on the glass so from
Speaker 1: the camera's perspective the polls were hidden. His process also
Speaker 1: involved double exposures. This was an example of a Matt painting,
Speaker 1: and he would claim credit for inventing this, and he
Speaker 1: even applied for a patent on it, but subsequent lawsuits
Speaker 1: established other filmmakers were using similar approaches, and the patent
Speaker 1: office ultimately denied the claim, but Matt paintings would become
Speaker 1: an important part of filmmaking from that point forward. One
Speaker 1: disadvantage to these early film effects was they required the
Speaker 1: camera to remain stationary that the whole process. You couldn't
Speaker 1: move the camera at all or else your shots wouldn't
Speaker 1: line up, so you wanted the camera to remain in
Speaker 1: one place through all of these different exposures. Another problem
Speaker 1: was that no action could cross the Matt line because
Speaker 1: it would get cut off as it moved beyond that
Speaker 1: invisible at least from the audience's perspective line. Now, let's
Speaker 1: move on up to nine eighteen, when a guy named
Speaker 1: Frank Williams created the Williams process, which honestly seems pretty
Speaker 1: convenient to me. The Williams process allowed for more movement
Speaker 1: and involved shooting actors against a solid background, such as
Speaker 1: a black or blue curtain on very high contrast film.
Speaker 1: The process sometimes required multiple transfers onto new film until
Speaker 1: you arrived at a black silhouette against a pure white background,
Speaker 1: the negative image of what you were shooting before, and
Speaker 1: this was called a holdout matt. The way these transfers
Speaker 1: typically would work is that you would put one strip
Speaker 1: of shot developed film into a camera, so you've already
Speaker 1: shot on it, but you're putting it through the camera again,
Speaker 1: and you would put a second strip of film that
Speaker 1: is unshot, it's unprocessed, no no lights hit it, and
Speaker 1: put it right up against the first developed piece of film,
Speaker 1: you would shine light through the camera and you would
Speaker 1: let it just run, and this way you would transfer
Speaker 1: the images from one strip to the other. And this
Speaker 1: was called by packing because you were putting two different
Speaker 1: pieces of film through the camera to achieve this process.
Speaker 1: And you could also do this not just with developed
Speaker 1: film where you're making copies. You could do it with negatives.
Speaker 1: You could do it in a way to increase contrast
Speaker 1: from copy to copy, until you were able to create
Speaker 1: a holdout matt. Reverse printing the holdout Matt creates a
Speaker 1: white silhouette on a black background or a cover mat.
Speaker 1: So now you've got to hold out Matt and a
Speaker 1: cover matt. You would take the footage of a previously
Speaker 1: shot background. Let's say it's a foreboding forest. So you've
Speaker 1: shot your actors in a sound stage, but you want
Speaker 1: the background to be this really scary looking forest, and
Speaker 1: you would bypack a film and camera with the background
Speaker 1: footage that you had shot and the black silhouette holdout
Speaker 1: Matt of the actor's footage that you shot. Then you
Speaker 1: would transfer this combination to a third piece of unexposed
Speaker 1: film by again shining a light through those other two
Speaker 1: pieces and because the background on the holdout mat is white,
Speaker 1: the light passes through it easily and it hits the
Speaker 1: previously shot background image that comes through and gets copied
Speaker 1: onto the blank film. The silhouette of your actors is
Speaker 1: black that prevents light from passing through. So the previously
Speaker 1: blank third piece of film now has a background image
Speaker 1: and this dark silhouette of actors moving through the frame.
Speaker 1: Then you would have to take that piece of film
Speaker 1: that has this black silhouette and you have to bypack
Speaker 1: it with the original footage of the actor, not the silhouette,
Speaker 1: but the actual actor footage. And now the real actor
Speaker 1: is on top of the silhouette and appears to actually
Speaker 1: be in front of whatever the background images, in our case,
Speaker 1: the foreboding forest. Because this type of matt moves from
Speaker 1: frame to frame, it's called a traveling matt. And if
Speaker 1: you remember Fraggle Rock, you might remember traveling matt is
Speaker 1: the name of go Bo's uncle. Gobo, by the way,
Speaker 1: is another stage in lighting term. It stands for a
Speaker 1: template or stencil that controls the shape of a lamps
Speaker 1: emitted light. So some of the Fraggles had fun industry
Speaker 1: names Gobo and traveling Matt. When we come back, we
Speaker 1: will continue down the history of how chroma key came about,
Speaker 1: but first let's take a quick break. Before the break,
Speaker 1: I was talking up the Williams process, but see Dodge
Speaker 1: Dunning would improve upon the Williams process by using yellow
Speaker 1: light to shoot the actor in front of a blue screen,
Speaker 1: creating the Dunning process. And this was used extensively in
Speaker 1: the classic nineteen thirty three film King Kong, and they
Speaker 1: weren't great for black and white film. Remember this is
Speaker 1: before anyone was shooting on color. So although I mean
Speaker 1: there were ways of treating film to create color, but
Speaker 1: this was standard black and white film, so he didn't
Speaker 1: have to worry about the weird lighting. But if you
Speaker 1: wanted to shoot in color, that was gonna cause require
Speaker 1: other considerations. Around the same time, engineers were developing the
Speaker 1: optical printer, which really simplified the process of transferring images
Speaker 1: from one strip of film to another. And I had
Speaker 1: talked about by packing, but the optical process could be
Speaker 1: an alternative to that. It didn't eliminate it, but it
Speaker 1: was a different way to achieve the same thing. Essentially,
Speaker 1: an optical printer has a projector on one side and
Speaker 1: a camera. On the other the projector shoots at the
Speaker 1: projected image that then gets copied onto a new unexposed
Speaker 1: role of film inside the camera. And it also allowed
Speaker 1: filmmakers to create new effects by changing the focal point
Speaker 1: of the camera or the distance between the projector and
Speaker 1: the camera, and rather than bypacking camera, you just use
Speaker 1: this process you could get better results. The first mass
Speaker 1: produced optical printer hit the market in the mid nineteen
Speaker 1: forties came from a company called Acme Done. In addition,
Speaker 1: filmmakers created rear projection background so in these actors would
Speaker 1: perform in front of a screen like a projection screen,
Speaker 1: not a green screen or a blue screen, and behind
Speaker 1: that screen would be a film projector and it would
Speaker 1: provide a projected background image. You could do this in
Speaker 1: place of the processes have already described, putting your actors
Speaker 1: in front of a screen that shows whatever background you
Speaker 1: wanted in the background could be fairly static, but didn't
Speaker 1: have to be. You could include a background that was
Speaker 1: actually dynamic, showing movement. It could be a film in
Speaker 1: of itself. This was used a lot in shots where
Speaker 1: people were in vehicles and talking with one another, so
Speaker 1: rather than setting up a car on a trailer and
Speaker 1: shooting it in the real world with the camera on
Speaker 1: the trailer, or or worse yet, trying to figure out
Speaker 1: how to fit a camera onto a real moving car
Speaker 1: that's operated by an actor. You would typically have performance
Speaker 1: sitting in a stationary vehicle, and the screen behind and
Speaker 1: sometimes to either side of them would display previously shot
Speaker 1: footage of scenery going by from the correct perspective, as
Speaker 1: if the car were driving down the road. This wasn't
Speaker 1: necessarily convincing, mind you, but it was an interesting technique.
Speaker 1: In ninety two, engineers created a process to produce films
Speaker 1: and color called appropriately Technicolor. Interestingly, in this process, images
Speaker 1: would be captured to three strips of black and white film.
Speaker 1: At this stage is the try strip approach. This was
Speaker 1: not the original version of Technicolor. It was technically the
Speaker 1: fourth incarnation of the Technicolor technology, but it's the important
Speaker 1: one for our discussion. So how do you produce a
Speaker 1: color image if you're using black and white film as
Speaker 1: your medium, Well, first you have to shoot your footage
Speaker 1: and inside an early technic color tri strip camera. Behind
Speaker 1: the lens was an optical cube and it acted as
Speaker 1: a prism prisms break up incoming light into bands of frequencies,
Speaker 1: and you've likely had one, or played with one, or
Speaker 1: at least seen one. That's the kind of stuff, you know.
Speaker 1: The light goes through it and then it makes rainbows.
Speaker 1: You see a little rainbow pattern projected somewhere. This prism
Speaker 1: would break up the incoming light into three general bands
Speaker 1: that corresponded with red, green, and blue. Each of those
Speaker 1: bands of light would hit one of three strips of
Speaker 1: black and white film inside the camera, So one strip
Speaker 1: of film would be exposed to all the red light
Speaker 1: coming from a scene, one from all the green light
Speaker 1: coming from a scene, one from the blue. The concentration
Speaker 1: of each color in the scene would affect how much
Speaker 1: light was hitting each strip of film, so you'd end
Speaker 1: up with three negatives of your scene that we're all
Speaker 1: perfectly synchronized, all of them in black and white, but
Speaker 1: each with different levels of brightness for different objects. It
Speaker 1: all depended on what color the objects were in the scene.
Speaker 1: A red chair, for example, would appear as a very
Speaker 1: prominent image on the black and white film that was
Speaker 1: hit with the red light, while it would be less
Speaker 1: noticeable in the green and blue strips. Now you would
Speaker 1: develop the negatives, and you would process the film, the
Speaker 1: three strips of film, and you would print them just
Speaker 1: as you would a regular black and white movie, and
Speaker 1: you would technically have three identical black and white sequences
Speaker 1: that only well, not identical, because the brightness would be
Speaker 1: different between each, but they would be of the exact
Speaker 1: same shot. You would then process these film strips by
Speaker 1: dying each of them in their respective color, so you
Speaker 1: would literally end up with a red tinted strip of film,
Speaker 1: blue tinted strip of film, and a green tinted strip
Speaker 1: of film. Then you would take these three dyed strips
Speaker 1: of film and you would laminate them together, and you
Speaker 1: would print that to a new role of film, and
Speaker 1: you would have a color motion picture which was fairly accurate,
Speaker 1: although the technical process would evolve over time to become
Speaker 1: even more so. And the technicolor process is really what
Speaker 1: set the stage for the next part of our story.
Speaker 1: It's why I felt the need to even explain how
Speaker 1: it worked. Now we get to a guy named Lawrence
Speaker 1: Larry Butler. He was born in nineteen o eight and
Speaker 1: he was actually a second generation optical effects professional. His father,
Speaker 1: William Butler, had been a silent film actor who frequently
Speaker 1: appeared indeed w Griffith Films. Larry worked on several motion
Speaker 1: pictures in the nineteen thirties before creating a new compositing
Speaker 1: process in for the film The Thief of Baghdad. In
Speaker 1: that film, Butler introduced a new special effect approach, and
Speaker 1: this would be the birth of the blue screen. All right,
Speaker 1: So let's break down this process. It builds on Technicolor,
Speaker 1: as I mentioned. So with Technicolor, you get three prints
Speaker 1: of your shot right, one for red, one for green,
Speaker 1: one for blue. If you created a solid backdrop in
Speaker 1: one of those three colors and shot something in front
Speaker 1: of that background, you could use that particular strip of
Speaker 1: film to create a traveling matt. Remember, the color would
Speaker 1: show up as very bright in your black and white
Speaker 1: film print because a lot of light is reflecting off
Speaker 1: of that particular color. Effectively, you could make a negative
Speaker 1: image of whatever the foreground was. The stuff you're shooting
Speaker 1: would be dark and the background would be bright. You
Speaker 1: would have to make sure that nothing in the scene
Speaker 1: had the same color, however, or else You're traveling matt
Speaker 1: would effectively have holes in it because the color of
Speaker 1: the foreground would match the color of the background. You've
Speaker 1: probably seen this, if someone's ever worn a shirt that's
Speaker 1: the same color as whatever screen they're supposed to be
Speaker 1: standing in front of. The same thing would even happen
Speaker 1: in film. It's just that it would happen well in
Speaker 1: advance of anyone being able to see it happen, like
Speaker 1: see the effect of it. Because you had to do
Speaker 1: all this other processing. The other two strips of black
Speaker 1: and white film would have pretty dark backgrounds because the
Speaker 1: light projected onto them wouldn't match the color of the backdrop,
Speaker 1: right uh. And you could take the film of a
Speaker 1: background shot. This is called the background plate, So this
Speaker 1: is previously shot film of whatever it is, whatever setting
Speaker 1: you're planning on putting this stuff, and then you use
Speaker 1: the traveling matt against it in an optical printer, and
Speaker 1: that would produce a silhouette of the foreground action. And
Speaker 1: it's that black hole that's the shape of whatever it
Speaker 1: was you were shooting. You would take this new print
Speaker 1: in which you've got the silhouette of your actually it's
Speaker 1: the previously filmed backdrop, and combined that with the processed
Speaker 1: color film to fill in that hole left by the
Speaker 1: traveling Matt. So you've got this possibility now of creating
Speaker 1: a traveling mat by taking advantage of the technicolor process.
Speaker 1: But then you have to make a decision which of
Speaker 1: the three colors should be the focus. Whichever color you
Speaker 1: choose is going to determine what you can shoot, because
Speaker 1: you can't have any objects or people in the scene
Speaker 1: that have that color on them, or the traveling mat
Speaker 1: won't work properly. This is what I mean when I say,
Speaker 1: if you've ever seen someone on screen news had a
Speaker 1: background effect bleed onto them because the color of clothing
Speaker 1: they're wearing, what was letting it happen? You've seen that issue.
Speaker 1: So Butler decided to go with blue as the backdrop color,
Speaker 1: largely because he determined it was a color far removed
Speaker 1: from skin tones, and he wanted to make sure that
Speaker 1: actors wouldn't match the color of the background and mess
Speaker 1: everything up. So as long as you weren't shooting anything
Speaker 1: blue in the foreground, you could use this process to
Speaker 1: make a composite image of the foreground action against a
Speaker 1: different background. He also would combine the blue negative image
Speaker 1: with the green positive or processed image to create a
Speaker 1: better traveling Matt something a more solid silhouette. In other words,
Speaker 1: Butler's contribution led to him winning an Academy Award for
Speaker 1: this process. Still, this was an incredibly time consuming approach.
Speaker 1: I'm sure you've gathered that just from my explanation of it.
Speaker 1: Because you had to shoot your sequence, you had to
Speaker 1: create the traveling matt negative, you had to combine that
Speaker 1: against the background footage, and you had to combine that
Speaker 1: combination of the background image and the traveling matt with
Speaker 1: the fully processed color image and then ultimately come up
Speaker 1: with a composite piece of film. It gave filmmakers way
Speaker 1: more options when making movies. It allowed them to shoot
Speaker 1: stuff inside a sound stage rather than whatever location they
Speaker 1: would have to go to, and even opened upe locations
Speaker 1: that would otherwise be impossible. But it did require a
Speaker 1: lot of post production time and work. It also required
Speaker 1: a close attention to lighting, otherwise you would end up
Speaker 1: with blue halos around people and that was pretty darn
Speaker 1: distracting effect. All of these different approaches required really good lighting,
Speaker 1: sometimes really intense lighting, so it would also create pretty
Speaker 1: uncomfortable shooting conditions that would get really hot in those
Speaker 1: sound stages. So while it was phenomenal technology. It required
Speaker 1: a lot of finesse to use it properly, and a
Speaker 1: human touch was absolutely necessary through every stage of the process. Now,
Speaker 1: over the next several years, really decades, movies benefited from
Speaker 1: this technology. The tech allowed filmmakers to do all sorts
Speaker 1: of neat things. Not only could they make it seem
Speaker 1: like actors were in places that would be hard or
Speaker 1: difficult to shoot in or places it maybe don't even exist,
Speaker 1: they also allowed for stuff like the incorporation of animation
Speaker 1: and live action in a way that wasn't really possible before.
Speaker 1: I'll get back to that again in a second. But
Speaker 1: in the early nineteen fifties, Eastman Kodak created the color
Speaker 1: motion picture film that simplified the process of shooting on
Speaker 1: color significantly so, rather than exposing three strips of black
Speaker 1: and white film two different bands of light, and then
Speaker 1: processing them to create a composite color image, this new
Speaker 1: film actually contained all the layers that corresponded to blue, green,
Speaker 1: and red. They each had essentially filters and dies in them,
Speaker 1: and each layer effectively had its own silver halide crystals
Speaker 1: and respective dies and streamlining the process for shooting on
Speaker 1: and developing color film you just had to have one strip,
Speaker 1: not the tri strip approach of technic color. It really
Speaker 1: changed things. Also, by tweaking the blue screen process, some
Speaker 1: inventors were able to get spectacular results. This gets us
Speaker 1: back to that live act an animation discussion. That would
Speaker 1: be Petro Vlajos, who was the engineer who worked on
Speaker 1: a little film called Mary Poppins in the early nineteen sixties.
Speaker 1: Law Hosts wanted to improve upon the technology that Butler
Speaker 1: had created, and one of the issues he sought to
Speaker 1: address was that the color blue used for blue screens
Speaker 1: wasn't a specific wavelength of light. You gotta remember that
Speaker 1: the wavelength of light, or if you prefer the frequency
Speaker 1: of light, the two are related, determines the lights color,
Speaker 1: the color that we perceive, and the wavelengths corresponding to
Speaker 1: the blue screens of the day ranged from four hundred
Speaker 1: thirty five nanometers to five hundred nanometers, and that meant
Speaker 1: any color blue that fell in or near that range
Speaker 1: was awful limits for use in a scene. Vlahos figured
Speaker 1: there had to be a better way, and he decided
Speaker 1: to use a different backdrop color entirely yellow, but not
Speaker 1: just any yellow. He wanted a precise yellow, the yellow
Speaker 1: that comes from sodium gas discharge lamps. When you excite
Speaker 1: sodium gas, essentially when you energize it with electricity, the
Speaker 1: gas gives off a distinct yellow light with a wavelength
Speaker 1: of five nine nanometers. As long as nothing in the
Speaker 1: camera frame matches that precise shade of yellow, you could
Speaker 1: have all sorts of colors in the shot, including different
Speaker 1: shades of yellow, and not have to worry about skimping
Speaker 1: on things like blue costume pieces. Paired with this was
Speaker 1: a customized camera that contained a prism that could isolate
Speaker 1: the five nine wavelength of light. Vlaw host was able
Speaker 1: to produce an incredibly precise and accurate traveling matt this way,
Speaker 1: which meant Disney could place actors on any separate background
Speaker 1: without worrying about the effect showing at the seams. In fact,
Speaker 1: in one sequence, Mary Poppins is wearing a hat that
Speaker 1: has this veil like material on it, and you can
Speaker 1: actually see the background, the anime background, through the veil,
Speaker 1: and that's because of the precision of this approach. There
Speaker 1: was one small hiccup, which was that vlaw host only
Speaker 1: had one working prism that could isolate this specific band
Speaker 1: of light. This fi nine nanometer band of light, so
Speaker 1: they only had one sodium vapor camera as a result. Now,
Speaker 1: when we come back, we're going to look at the
Speaker 1: further evolution of this technology, including how it has changed
Speaker 1: once the digital realm became a reality. But first let's
Speaker 1: take another quick break. I've stuck with the film world
Speaker 1: for this podcast so far, but I also have to
Speaker 1: talk about the use of chroma key technology in the
Speaker 1: world of live television. See Mary Poppins came out in
Speaker 1: nineteen sixty four, but the first use of chroma key
Speaker 1: on live TV was in the late nineteen fifties. This
Speaker 1: is the same technology that would become the basis for
Speaker 1: TV weather reports, where the meteorologist stands in front of
Speaker 1: a wall which seems to have a dynamic map on
Speaker 1: it that can change from one image to the next.
Speaker 1: But if the process I've described required so many steps,
Speaker 1: if you had to do so much post production on
Speaker 1: the film, how could you take that same basic idea
Speaker 1: and make it work in the realm of television in
Speaker 1: real time live broadcast. Frank Gaskins and Mitt Altman led
Speaker 1: this effort at NBC in the nineteen fifties. They created
Speaker 1: a television camera approach to chromakey and tested it out
Speaker 1: in nineteen fifty seven with a live broadcast of Matinee Theater.
Speaker 1: The specific story they chose to serve as the first
Speaker 1: experiment here was an adaptation of The Invisible Man, and
Speaker 1: that was fitting because the nineteen thirty three film adaptation
Speaker 1: of The Invisible Man had relied heavily on the old
Speaker 1: Williams process. The live television version initially relied on two cameras.
Speaker 1: One camera would capture a background image. The other camera
Speaker 1: would be the foreground camera that would be for all
Speaker 1: the action in the sequence, and behind all this action
Speaker 1: would be a lou backdrop. Combining these two sets of
Speaker 1: images simultaneously in a device called a chroma key amplifier
Speaker 1: would create a live composite video feed. Engineers at our
Speaker 1: c A created the actual technology, and I think it's
Speaker 1: best if I just quote directly from the nineteen edition
Speaker 1: of the journal Electronic Age that describes this process. So
Speaker 1: here's a quote. A switching signal or a color key
Speaker 1: used in association with the special effects amplifier controls the
Speaker 1: signals sent out over the air. The switching signal is
Speaker 1: in turn created by the camera photographing the live action
Speaker 1: in front of the blue screen. While the camera is
Speaker 1: scanning the blue screen, the switching device automatically activates the
Speaker 1: second camera, which projects the background. When the scanning signal
Speaker 1: reaches an area covered by the live actors, the switching
Speaker 1: device turns off the camera projecting the background material and
Speaker 1: transmits the action. Now that's the end of that quote.
Speaker 1: You could also feed images directly to the chroma key amplifier.
Speaker 1: It didn't have to be a live video from a
Speaker 1: second camera, so you could provide an image like a map,
Speaker 1: allowing a meteorologist to stand in front of it otherwise
Speaker 1: blank blue or green screen and gesture at various regions.
Speaker 1: The audience at home would see the meteorologist appearing to
Speaker 1: stand in front of the map, or maybe a summary
Speaker 1: of the forecasted whether for the week, and not just
Speaker 1: a blue screen or a green screen. Around the nineteen seventies,
Speaker 1: that's when we started to see a gradual shift, particularly
Speaker 1: in television, from blue screens to green ones. Part of
Speaker 1: that was because of a very slow transition into digital technology.
Speaker 1: It would become more important as digital cameras became a thing.
Speaker 1: Digital cameras were better attuned to doing this with greens
Speaker 1: rather than with blues, although you can do either. But
Speaker 1: another big reason was just that people don't tend to
Speaker 1: wear a lot of green, whereas blue was a pretty
Speaker 1: and still is a pretty popular color. And once in
Speaker 1: a while, so when on camera would forget that they're
Speaker 1: wearing blue, and then they'd step in front a blue
Speaker 1: screen and suddenly their jacket or their shirt or their
Speaker 1: tie or whatever would become part of the background image.
Speaker 1: Back to film for a moment. We're gonna leave TV
Speaker 1: for a second. In nineteen eighty a guy named Richard Edlund,
Speaker 1: who worked on a little film called The Umpire Strikes Back,
Speaker 1: made another big contribution to the chroma key process. Edlund
Speaker 1: developed a quad optical printer which both sped up the
Speaker 1: process for producing composite film shots and also brought the
Speaker 1: price down as well. I mean, if you think about it,
Speaker 1: saving time means saving money. He also developed a computer
Speaker 1: controlled system of cameras which allowed for very precise camera movements,
Speaker 1: and that meant you could create choreographed shots of foreground
Speaker 1: and background and composite them together and have the match
Speaker 1: up perfectly. It was also really effective for processing images
Speaker 1: that were shot with miniatures, which was done a lot
Speaker 1: in the original Star Wars series, so it was still
Speaker 1: a painstaking process, but now a lot more could be
Speaker 1: done on one piece of equipment per pass, as opposed
Speaker 1: to having to do a process on the piece of
Speaker 1: equipment then do it again and then again and again
Speaker 1: until you finally got whatever result you were after. Gradually,
Speaker 1: computer software would creep into the realm of film and
Speaker 1: video effects, and this leads us to a version of
Speaker 1: chroma key that I think is actually the easiest to understand.
Speaker 1: It's it's technically advanced, but the principle is simple. So
Speaker 1: let's say that you want to do a Twitch stream
Speaker 1: and you're playing a video game live, and you want
Speaker 1: your viewers to see you sitting in front of the
Speaker 1: video game footage. So wants to make a dynamic background
Speaker 1: of video gameplay behind you. So you go out and
Speaker 1: you buy a green screen and you set it up
Speaker 1: behind your gaming chair, You throw up some lights. More
Speaker 1: on that in a second, and you launch a program
Speaker 1: that will insert your video game capture as a custom
Speaker 1: digital background. Your viewers will see you sitting in front
Speaker 1: of a screen otherwise filled with I don't know, Skyrim
Speaker 1: or Minecraft or the untitled Goose game or whatever it
Speaker 1: is you're playing. What's going on on a technical level, Well,
Speaker 1: the digital world is different from the analog world in
Speaker 1: lots of ways, But importantly for our discussion, it comes
Speaker 1: down to how in the digital world everything ultimately boils
Speaker 1: down to numeric values. You or I could have a
Speaker 1: debate about whether a particular color is aquamarine versus arrow blue,
Speaker 1: versus blue green versus dark cyan, or whatever it may be.
Speaker 1: But in the digital world, every color ultimately has a
Speaker 1: numeric value. Assuming whatever we're looking at is a solid color,
Speaker 1: you could designate that solid color with a specific numeric
Speaker 1: value in computer software and then replicated it or immediately
Speaker 1: identify it within any scene you might see where I'm
Speaker 1: going here. With video software, you can designate a specific
Speaker 1: color from one video source. Uh, this specific color is
Speaker 1: the chroma, as it were, and this is the color
Speaker 1: you want to replace or key out. The video software
Speaker 1: analyzes information that's coming from say a digital camera feed
Speaker 1: into your computer, and it looks for any signals that
Speaker 1: map to the value or values of the color or
Speaker 1: colors you've picked. Most software lets you fine tune this
Speaker 1: so you can adjust the settings to hone in on
Speaker 1: the specific shade of green or blue or whatever it
Speaker 1: is that you plan to key out. Anything that matches
Speaker 1: that value or range of values then gets turned into
Speaker 1: a transparent video layer. The secondary image. In our case,
Speaker 1: the video game footage that we're creating as we're playing
Speaker 1: this game shows through this transparent layer, and you can
Speaker 1: actually think of the foreground video as an overlay on
Speaker 1: top of the digital background layer the video game footage.
Speaker 1: Anything transparent in that overlay will show the background through
Speaker 1: the solid stuff. Presumably you, the Twitch player, will block
Speaker 1: the background image, so viewers will be able to see
Speaker 1: their favorite Twitch streamer sitting in front of a video game.
Speaker 1: The software does all the work for you, creating the
Speaker 1: composite video feed that the viewer sees. That software, by
Speaker 1: the way, isn't Twitch itself. Twitch is a video streaming platform,
Speaker 1: but to actually do these sort of effects, you'd need
Speaker 1: to use some other piece of software, such as some
Speaker 1: version of Open Broadcasters Software or o b S, And
Speaker 1: there are a lot of different versions of video broadcasting
Speaker 1: software available for folks to play with, from free stuff
Speaker 1: to professional grade stuff. This type of versatility is the
Speaker 1: kind of stuff that previously you would have had to
Speaker 1: have worked in like a TV studio to have access to,
Speaker 1: but now anyone with a sufficiently beefy computer can run
Speaker 1: this kind of operation. For this to work well, you
Speaker 1: want to have really good lighting, both for the foreground
Speaker 1: and for the background drop. You want the lighting on
Speaker 1: the green screen you're using to be nice and even,
Speaker 1: and you want to eliminate any shadows, because if you're
Speaker 1: casting a shadow on the green screen, the camera will
Speaker 1: pick up that part of the green screen as being
Speaker 1: a darker color, and it might even be dark enough
Speaker 1: that the video software doesn't identify it as the color
Speaker 1: that you want to key out. So in those cases
Speaker 1: you would get these weird video artifacts on screen as
Speaker 1: a result, it be really distracting. So ideally you want
Speaker 1: lights that will illuminate the green screen evenly and are
Speaker 1: dedicated just for that purpose. If you're lighting yourself directly
Speaker 1: from the front, you're not using a ring light or
Speaker 1: anything like that, then you're gonna be casting a shadow
Speaker 1: behind you, unless you're Peter Pan, in which case I
Speaker 1: guess you just think cappy thoughts. Now, this flies for
Speaker 1: stuff like zoom meetings and Twitch streams, but when it
Speaker 1: comes to professional grade film, it's not really up to snuff.
Speaker 1: Software can do a bulk of the work, but good
Speaker 1: old human effects artists are still needed to make sure
Speaker 1: everything is coming out well. They can step in and
Speaker 1: do some quality control. They can tweak things, they can
Speaker 1: fix any issues that pop up, and that pays off.
Speaker 1: You've probably seen a movie that had phenomenal attention to
Speaker 1: this process and the effects are top notch. And you've
Speaker 1: probably seen other movies where, due to whatever reason, maybe
Speaker 1: it was budget, maybe it's just the talent of the
Speaker 1: people working on it, you could tell that such care
Speaker 1: wasn't given to the process and it shows in the
Speaker 1: final product. I still think films like Jurassic Park I'm
Speaker 1: talking about the original Jurassic Park hold up pretty darn well.
Speaker 1: And part of that is that the movie depended on
Speaker 1: a mixture of different effects. Some of them were computer
Speaker 1: generated and keyed in, some were robotic effect x But
Speaker 1: a lot of this has to do with the fact
Speaker 1: that the effects team as a whole took tremendous care
Speaker 1: to produce results that were really convincing to the eye.
Speaker 1: And that's the story behind chroma key and green or
Speaker 1: blue screen technology. It's a super interesting approach to creating
Speaker 1: a composite moving image. And frankly, there's gonna be a
Speaker 1: lot of other topics around this that I can go into.
Speaker 1: I could probably talk even more about optical printers, for example,
Speaker 1: and the various approaches to film processing. And you can
Speaker 1: see that while the actual chroma key process is very
Speaker 1: different between film and digital video, the basic idea of
Speaker 1: replacing one color or one element in a shot was
Speaker 1: something from a totally different source remains the same. It's
Speaker 1: the same underlying principle no matter what the actual process is.
Speaker 1: If you guys have suggestions for future topics I should
Speaker 1: cover here on tech stuff, whether it's a specific technology,
Speaker 1: a company in tech, a personality in tech, maybe it's
Speaker 1: just a trend in tech in general, reach out to
Speaker 1: me let me know what I should cover. You can
Speaker 1: get in touch through Twitter or Facebook. The hand over
Speaker 1: both of those is text stuff H s W and
Speaker 1: I'll talk to you again really soon. Text Stuff is
Speaker 1: an I Heart Radio production. For more podcasts from My
Speaker 1: Heart Radio, visit the I Heart Radio app, Apple Podcasts,
Speaker 1: or wherever you listen to your favorite shows.