Speaker 1: Welcome to tech Stuff, a production from iHeartRadio. Hey Thearon,
Speaker 1: Welcome to tech Stuff. I'm your host, Jonathan Strickland. I'm
Speaker 1: an executive producer with iHeart Podcasts. And how the tech
Speaker 1: are you well? Here in the United States, we are
Speaker 1: celebrating Thanksgiving, which means our office is closed, so I
Speaker 1: do not have a brand new episode for you, but
Speaker 1: I do have a pretty cool episode that we published
Speaker 1: on June one, twenty twenty. It is titled tech Stuff
Speaker 1: in front of a Green Screen. So I hope you enjoy.
Speaker 1: And for those of you who are celebrating, Happy Thanksgiving,
Speaker 1: and for those of y'all not in the United States,
Speaker 1: maybe in Canada where you had Thanksgiving already. To you,
Speaker 1: I say happy Thursday, enjoy this rerun episode of tech Stuff.
Speaker 1: Today's topic goes by many names like chroma key, or
Speaker 1: blue screen or green screen. The inventor of this technology
Speaker 1: developed it for film, and that pun was unintentional, you know,
Speaker 1: developed for film, but I'm gonna run with it. Today
Speaker 1: we use this technology in 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 soundstage. But today there are a lot of
Speaker 1: folks who have a green screen just stashed in their
Speaker 1: 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 modus oparandi, let's give a
Speaker 1: quick overview of what this technology actually does. So it's
Speaker 1: a system that allows a creator to insert images, typically
Speaker 1: a background that's your standard use of this, and you
Speaker 1: do it into a shot that otherwise isn't actually in
Speaker 1: that location, so it could be a static image, or
Speaker 1: the new image might be in motion itself, so it
Speaker 1: might be video or film. This technology allows creators to
Speaker 1: shoot in locations they might otherwise have trouble getting to,
Speaker 1: like the bottom of the ocean or an outer space,
Speaker 1: or in my old college dorm room because I was
Speaker 1: notorious for locking myself out. So when you do it well,
Speaker 1: it really enhances a scene. But when done poorly, it's
Speaker 1: incredibly distracting because it's so obvious that the people or
Speaker 1: you know whatever that are in the foreground of the
Speaker 1: shot aren't actually in whatever the environment is. But that's
Speaker 1: the basic idea. It's to create a composite, a combination
Speaker 1: of multiple shots into a single new shot, so that
Speaker 1: the component and it's 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 coating 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 gelatine and grains of silver halid crystals, which react
Speaker 1: to the light. These are those photosensitive chemicals and also
Speaker 1: some special molecules that bind with silver haylid 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: haylight crystals coating 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 plastic. 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 are ready to take your image. Then
Speaker 1: you open the shutter. This exposes that piece of film
Speaker 1: to the light that's being reflected off of whatever it
Speaker 1: is you're photographing. Remember when we see things, we're seeing
Speaker 1: light bouncing off of that and the color of the
Speaker 1: stuff we see is dependent upon and which frequencies of
Speaker 1: light bounce off of that thing. So then the shutter
Speaker 1: closes on your camera and you've got your chemical record.
Speaker 1: And the shutter is necessary because, as I said, these
Speaker 1: chemicals react to light. If you just had this stuff
Speaker 1: exposed to light all the time, it would have already reacted.
Speaker 1: You would not be able to use it to take
Speaker 1: a photograph of anything if you want to learn more
Speaker 1: about this process, which is fascinating, but really the process
Speaker 1: of photography is far enough out of the scope of
Speaker 1: this episode that I don't want to go into it
Speaker 1: much further. I do recommend you go to HowStuffWorks dot com.
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 up the article how Photographic Film Works.
Speaker 1: It was written by Chuck Woodworth and it's a great
Speaker 1: example of the how Stuffworks style, and it goes into
Speaker 1: the chemistry and physics of the photographic process, but we'll
Speaker 1: skim over the rest of that for the purpose of
Speaker 1: this episode. So now the film on the camera has
Speaker 1: a latent image on it, and it represents the moment
Speaker 1: in time the shutter allowed light to pass from the
Speaker 1: lens to hit the film. But in a film camera,
Speaker 1: a cinema camera, you're talking about a series of latent images.
Speaker 1: Motors pull this strip of film at a steady speed
Speaker 1: through the frame of the camera, where the shutter opens
Speaker 1: and closes at a regular frequency, and the standard speed
Speaker 1: of capturing images is twenty four frames per second. So
Speaker 1: a film camera is capturing twenty four photographs every second.
Speaker 1: The latent images need some processing in order to create
Speaker 1: something that can be fed through a film projector. The
Speaker 1: development process creates a negative image of the chemical record,
Speaker 1: and that means that the darkest areas of the image
Speaker 1: represent the spots where the film received the most light.
Speaker 1: It's the opposite of what you would expect, right. Anything
Speaker 1: that would be dark in a photograph will be light
Speaker 1: on a negative and vice versa. This negative has to
Speaker 1: be transferred onto another role of film to create a
Speaker 1: positive image in a process that I'm also not going
Speaker 1: to cover because we need some time for actual topic. Right.
Speaker 1: So when we watch a film, we have the perception
Speaker 1: that what we're viewing are moving objects up on a screen,
Speaker 1: but that is an illusion. What we're really seeing with
Speaker 1: true film is that it's a series of photographs. The
Speaker 1: projector is playing those photographs at the same speed that
Speaker 1: the film camera used to make them twenty four frames
Speaker 1: per second usually. I mean, if you want to play
Speaker 1: stuff in slow motion, then you would shoot a film
Speaker 1: at a much higher frame rate, like forty eight frames
Speaker 1: per second, but you would play it back at the
Speaker 1: standard twenty four frames per second, and that would give
Speaker 1: you the slow motion effect. And back in the old days,
Speaker 1: cameras were hand cranked, so you would get kind end
Speaker 1: of twenty four frames per second, but this would result
Speaker 1: in sort of that hurky jerky movement we associate with
Speaker 1: old movies that was hand cranked cinematography, and sometimes people
Speaker 1: would turn the crank a little faster or a little
Speaker 1: slower than others, so you don't really have a consistent
Speaker 1: experience there, because the playback speed, especially if you're playing
Speaker 1: it in a modern projector, is going to be standard,
Speaker 1: even if the recording speed wasn't. But never mind all that.
Speaker 1: If you were to stop the projector's reels at any
Speaker 1: given moment in the playback of a film, you would
Speaker 1: see a still image. You would advance the reel by
Speaker 1: one frame, and you would see the next image, the
Speaker 1: next photograph in that series, and you would likely be
Speaker 1: able to pick out how things are slightly different from
Speaker 1: the first frame you looked at and the next frame.
Speaker 1: And this is the same principle that's behind animation. If
Speaker 1: you've ever taken a pad of sticky notes and you
Speaker 1: drawn little figures on page after page after page that
Speaker 1: when you flip the pages, you get a simple little cartoon,
Speaker 1: then you've engaged in the same art form as great cinematographers.
Speaker 1: Then maybe your work was even better than theirs. I'm
Speaker 1: not one to judge. Now, why would I go to
Speaker 1: the trouble to cover the basics of film? Well, it's
Speaker 1: because the very nature of film inspired certain people to
Speaker 1: experiment with it, to try stuff that would be impossible
Speaker 1: to replicate in a real world setting, or at least
Speaker 1: it would be really difficult. Film wasn't a substitution for
Speaker 1: a theater. In theater, you can create a few interesting effects.
Speaker 1: Generally your options are limited to things like lighting tricks,
Speaker 1: maybe some creative sets or costumes, maybe an even a
Speaker 1: stage illusion or two, and perhaps some sound design. But
Speaker 1: with film there were other possibilities, and one fellow who
Speaker 1: recognized those possibilities was the French filmmaker and illusionist George Mellier.
Speaker 1: He was born in Paris, You know Paris in eighteen
Speaker 1: sixty one. Let that sink in for a moment. This
Speaker 1: man was born while the Civil War was going on
Speaker 1: in the United States. He became interested in stagecraft and magic,
Speaker 1: and by the eighteen nineties he was a successful stage magician.
Speaker 1: In eighteen ninety five, he saw an early film exhibition
Speaker 1: made by the Lumier Brothers and he became entranced by
Speaker 1: this new medium. His experience and illusions encouraged him to
Speaker 1: find ways to experiment with film to achieve new effects,
Speaker 1: stuff that wouldn't be possible to do in the real world.
Speaker 1: He was a special effects and film pioneer. He established
Speaker 1: methods to shoot slow motion, stop motion animation, to do dissolves,
Speaker 1: and tricks like superimposition and double exposure. Around eighteen ninety eight,
Speaker 1: Melier had a really cool idea. He wanted to create
Speaker 1: a truly bizarre special effect in which an actor would
Speaker 1: appear to remove his own head on screen. But how
Speaker 1: would he accomplish this? While the secret was in shooting
Speaker 1: multiple exposures of the same real film. Typically, after you
Speaker 1: expose film to light, you want to avoid doing that
Speaker 1: again because you will interfere with that chemical record. You know,
Speaker 1: if you were to ever take photographs with a film
Speaker 1: camera and then someone were to open up the back
Speaker 1: of the camera and expose the film to regular light,
Speaker 1: you could potentially ruin shots that were already made, plus
Speaker 1: ruin the film for the next couple of shots. It's
Speaker 1: not something that you typically want to do. More light
Speaker 1: will cause further reactions, chemical reactions on the actual plastic film,
Speaker 1: and your shot gets ruined. If you've ever used the
Speaker 1: cameras that don't quite line up the film properly at
Speaker 1: the very beginning or the very end, you might even
Speaker 1: notice that a couple of photos on those sections of
Speaker 1: the film role have two sets of images super imposed
Speaker 1: on top of one another, and that's because that little
Speaker 1: section of film was exposed more than once. Melia did
Speaker 1: this on purpose. He would set up a shot and
Speaker 1: he would use a lens that had some of the
Speaker 1: lens blacked out so that light could not pass through
Speaker 1: that part of the lens. And we refer to this
Speaker 1: as a mat matte, and you can think of it
Speaker 1: like a mask for the lens, and that would mean
Speaker 1: a section of each frame corresponding to that part of
Speaker 1: the mat would remain unexposed to light. He would shoot
Speaker 1: the scene as rehearsed. Afterward, he would rewind the exposed
Speaker 1: film in the camera, beat it right back in as
Speaker 1: if he was going to shoot something all for the
Speaker 1: first time, and he would then replace this mat with
Speaker 1: a new one and the new mat would block out
Speaker 1: everything except the section that previously was unexposed. So in
Speaker 1: other words, the part that was black would now be clear,
Speaker 1: and the rest of the lens that was previously unblacked
Speaker 1: would be blacked. So you replace one mat with a
Speaker 1: different one. So he would then be able to film
Speaker 1: something totally new into this same role of film, and
Speaker 1: this time the would pick up a new scene and
Speaker 1: by changing things between one section and the other, he
Speaker 1: could create weird effects like the head removal trick. It
Speaker 1: would appear as though all of this was shot at
Speaker 1: the same time on the same role of film, but
Speaker 1: in fact, through careful control of where the light would go,
Speaker 1: Melia would use the same film twice or more to
Speaker 1: produce cool results. And if you want to see an
Speaker 1: example of what I'm talking about, and I highly recommend
Speaker 1: you check this out because it is amazing even today,
Speaker 1: go to YouTube and do a search for the short
Speaker 1: film four Heads Are Better than One. The creativity of
Speaker 1: this film, which by the way, lasts less than a minute,
Speaker 1: is still astonishing. To say his experimental work was influential
Speaker 1: would be a gross understatement. Other filmmakers, inspired by the
Speaker 1: work of Melia tried new techniques that built upon the
Speaker 1: foundation he established. For example, filmmaker and documentarian Norman Dawn
Speaker 1: wanted to show 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: pane of glass between the camera and the scene he
Speaker 1: wanted to shoot, and on that pane of glass 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 so from the
Speaker 1: camera's perspective the polls were hidden. His process also involved
Speaker 1: 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 that other filmmakers were using similar approaches, and the
Speaker 1: patent office ultimately denied the claim, but Matt paintings would
Speaker 1: become an important part of filmmaking from that point forward.
Speaker 1: One disadvantage to these early film effects was they required
Speaker 1: the camera to remain stationary through the whole process. You
Speaker 1: couldn't move the camera at all, or else your shots
Speaker 1: wouldn't line up, so you wanted the camera to remain
Speaker 1: in one place through all of these different exposures. Another
Speaker 1: problem was that no action could cross the Matt line
Speaker 1: because it would get cut off as it moved beyond
Speaker 1: that invisible at least from the audience's perspective line. Now,
Speaker 1: let's move on up to nineteen eighteen, when a guy
Speaker 1: named Frank Williams created the Williams process, which honestly seems
Speaker 1: pretty convenient to me. The Williams process allowed for more
Speaker 1: movement and involved shooting actors against a solid background such
Speaker 1: as 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 lights hit it, and put
Speaker 1: 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: for the images from one strip to the other. And
Speaker 1: this was called bypacking 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 mat 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 a holdout matt and a cover mat.
Speaker 1: You would take the footage of a previously shot background.
Speaker 1: Let's say it's a foreboding forest, so you've shot your
Speaker 1: actors in a sound stage, but you want the background
Speaker 1: to be this really scary looking forest, and you would
Speaker 1: bypack a film camera with the background footage that you
Speaker 1: had shot and the black silhouette holdout matt of the
Speaker 1: actor's footage that you shot. Then you would transfer this
Speaker 1: combination to a third piece of unexposed film by again
Speaker 1: shining a light through those other two pieces. And because
Speaker 1: the background on the holdout mat is white, the light
Speaker 1: passes through it easily and it hits the previously shot
Speaker 1: background image that comes through and gets copied onto the
Speaker 1: blank film. The silhouette of your actors is black that
Speaker 1: prevents light from passing through. So the previously blank third
Speaker 1: piece of film now has a background image and this
Speaker 1: dark silhouette of actors moving through the frame. Then you
Speaker 1: would have to take that piece of film that has
Speaker 1: this black silhouette and you have to bypack it with
Speaker 1: the original footage of the actor, not the silhouette, but
Speaker 1: the actual actor footage. And now the real actor is
Speaker 1: on top of the silhouette and appears to actually be
Speaker 1: in front of whatever the background image is, 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 mat. And if
Speaker 1: you remember Fraggle Rock you might remember Traveling Matt is
Speaker 1: the name of Gobo's uncle. Gobo, by the way, is
Speaker 1: another stage and lighting term. It stands for a template
Speaker 1: or stencil that controls the shape of a lamps emitted light.
Speaker 1: So some of the Fraggles had fun industry names, Gobo
Speaker 1: and traveling Matt. When we come back, we will continue
Speaker 1: down the history of how chroma key came about. But
Speaker 1: first let's take a quick break. Before the break, I
Speaker 1: was talking about the Williams process, but C. Dodge Dunning
Speaker 1: would improve upon the Williams process by using yellow light
Speaker 1: 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 you didn't
Speaker 1: have to worry about the weird lighting. But if you
Speaker 1: wanted to shoot in color, that was going to cause
Speaker 1: or require other considerations. Around the same time, engineers were
Speaker 1: developing the optical printer, which really simplified the process of
Speaker 1: transferring images from one strip of film to another. Now
Speaker 1: I talked about bypacking, 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 out a
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 forties.
Speaker 1: It came from a company called Acme Donne. In addition,
Speaker 1: filmmakers created rear projection backgrounds, 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 wanted.
Speaker 1: The background could be fairly static, but didn't have to be.
Speaker 1: You could include a background that was actually dynamic, showing movement.
Speaker 1: It could be a film in of itself. This was
Speaker 1: used a lot in shots where people were in vehicles
Speaker 1: and talking with one another. So rather than setting up
Speaker 1: a car on a trailer and shooting it in the
Speaker 1: real world with the camera on the trailer, or worse yet,
Speaker 1: trying to figure out how to fit a camera onto
Speaker 1: a real moving car that's operated by an actor, you
Speaker 1: would typically have performers sitting in a stationary vehicle and
Speaker 1: the screen behind and sometimes to either side of them
Speaker 1: would display previously shot footage of scenery going by from
Speaker 1: the correct perspective, as if the car were driving down
Speaker 1: the road. This wasn't necessarily convincing, mind you, but it
Speaker 1: was an interesting technique. In nineteen thirty two, engineers created
Speaker 1: a process to produce films in color called appropriately Technicolor. Interestingly,
Speaker 1: in this process, images would be captured to three strips
Speaker 1: of black and white film at this stage as the
Speaker 1: tri strip approach. This was not the original version of Technicolor.
Speaker 1: It was technically the fourth incarnation of the Technicolor technology,
Speaker 1: but it's the important one for our discussion. So how
Speaker 1: do you produce a color image if you're using black
Speaker 1: and white film as your medium? Well, first you have
Speaker 1: to shoot your footage. And inside an early Technicolor tri
Speaker 1: strip camera behind the lens was an optical cube and
Speaker 1: it acted as a prism. Prisms break up incoming light
Speaker 1: into bands of frequencies, and you've likely had one, or
Speaker 1: played with one, or at least seen one. That's the
Speaker 1: kind of stuff, you know. A light goes through it
Speaker 1: and then it makes rainbows. You see a little rainbow
Speaker 1: pattern projected somewhere. This prism would break up the incoming
Speaker 1: light into three general bands that corresponded with red, green,
Speaker 1: and blue. Each of those bands of light would hit
Speaker 1: one of three strips of black and white film inside
Speaker 1: the camera, so one strip of film would be exposed
Speaker 1: to all the red light coming from a scene, one
Speaker 1: from all the green light coming from a scene and
Speaker 1: one from the blue. The concentration of each color in
Speaker 1: the scene would affect how much light was hitting each
Speaker 1: strip of film, So you'd end up with three negatives
Speaker 1: of your scene that were all perfectly synchronized, all of
Speaker 1: them in black and white, but each with different levels
Speaker 1: of brightness for different objects. It all depended on what
Speaker 1: color the objects were in the scene. A red chair,
Speaker 1: for example, would appear as a very prominent image on
Speaker 1: the black and white film that was hit with the
Speaker 1: red light, while it would be less noticeable in the
Speaker 1: green and blue strips. Now you would develop the negatives,
Speaker 1: and you would process the film, the three strips of film,
Speaker 1: and you would print them just as you would a
Speaker 1: regular black and white movie, and you would technically have
Speaker 1: three identical black and white sequences that only well, not
Speaker 1: identical because the brightness would be different between each, but
Speaker 1: they would be of the exact same shot. You would
Speaker 1: then process these film strips by dying each of them
Speaker 1: in their respective color, so you would literally end up
Speaker 1: with a red tinted strip of film, blue tinted strip
Speaker 1: of film, and a green tinted strip of film. Then
Speaker 1: you would take these three died strips of film, and
Speaker 1: you would laminate them together and you would print that
Speaker 1: to a new role of film and you would have
Speaker 1: a color motion picture which was fairly accurate, although the
Speaker 1: technical process would evolve over time to become even more so.
Speaker 1: And the Technicolor process is really what set the stage
Speaker 1: for the next part of our story. It's why I
Speaker 1: felt the need to even explain how it worked. Now
Speaker 1: we get to a guy named Lawrence Larry Butler. He
Speaker 1: was born in nineteen oh eight and he was actually
Speaker 1: a second generation optical effects professional. His father, William Butler,
Speaker 1: had been a silent film actor who frequently appeared in d. W.
Speaker 1: Griffith films. Larry worked on several motion pictures in the
Speaker 1: nineteen thirties before creating a new compositing process in nineteen
Speaker 1: forty for the film The Thief of Baghdad. In that film,
Speaker 1: Butler introduced a new special effect approach and this would
Speaker 1: be the birth of the blue screen. All right, So
Speaker 1: let's break down this process, and 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 mat. 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 your 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. Right,
Speaker 1: And you could take the film of a background shot.
Speaker 1: This is called the background plate. So this is previously
Speaker 1: shot film of whatever it is, whatever setting you're planning
Speaker 1: on putting this stuff, and then you use the traveling
Speaker 1: mat against it in an optical printer, and that would
Speaker 1: produce a silhouette of the foreground action. And it's that
Speaker 1: black hole that's the shape of whatever it was you
Speaker 1: were shooting. And you would take this new print in
Speaker 1: which you've got the silhouette of your action, it's the
Speaker 1: previously filmed backdrop, and combine that with the processed color
Speaker 1: film to fill in that hole left by the traveling mat.
Speaker 1: So you've got this possibility now of creating a traveling
Speaker 1: mat by taking advantage of the technicolor process. But then
Speaker 1: you have to make a decision which of the three
Speaker 1: colors should be the focus. Whichever color you choose is
Speaker 1: going to determine what you can shoot, because you can't
Speaker 1: have any objects or people in the scene that have
Speaker 1: that color on them, or the traveling matt won't work properly.
Speaker 1: This is what I mean when I say, if you've
Speaker 1: ever seen someone on screen who's had a background effect
Speaker 1: bleed onto them because the color of clothing they're wearing,
Speaker 1: what was letting it happen. You've seen that issue. So
Speaker 1: 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 tracking 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 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 matte 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 it even opened up
Speaker 1: locations that would otherwise be impossible. But it did require
Speaker 1: a lot of post production time and work. It also
Speaker 1: required a close attention to lighting, otherwise you would end
Speaker 1: up with blue halos around people and that was pretty
Speaker 1: aren't distracting. In fact, all of these different approaches required
Speaker 1: really good lighting, sometimes really intense lighting, so it would
Speaker 1: also create pretty uncomfortable shooting conditions. It would get really
Speaker 1: hot in those sound stages. So while it was phenomenal technology,
Speaker 1: it required a lot of finesse to use it properly,
Speaker 1: and a human touch was absolutely necessary through every stage
Speaker 1: of the process. Now, over the next several years, really decades,
Speaker 1: movies benefited from this technology. The tech allowed filmmakers to
Speaker 1: do all sorts of neat things. Not only could they
Speaker 1: make it seem like actors were in places that would
Speaker 1: be hard or difficult to shoot in or places that
Speaker 1: maybe don't even exist, they also allowed for stuff like
Speaker 1: the incorporation of animation and live action in a way
Speaker 1: that wasn't really possible. Before I'll get back to that again,
Speaker 1: in a second. But in the early nineteen fifties, Eastman
Speaker 1: Kodak created the color motion picture film that simplified the
Speaker 1: process of shooting on color significant So, rather than exposing
Speaker 1: three strips of black and white film to different bands
Speaker 1: of light and then processing them to create a composite
Speaker 1: color image, this new film actually contained all the layers
Speaker 1: that corresponded to blue, green, and red. They each had
Speaker 1: essentially filters and dyes in them, and each layer effectively
Speaker 1: had its own silver halide crystals and respective dyes, and
Speaker 1: streamlining the process for shooting on and developing color film.
Speaker 1: You just had to have one strip, not the tri
Speaker 1: strip approach of Technicolor. It really changed things. Also, by
Speaker 1: tweaking the blue screen process, some inventors were able to
Speaker 1: get spectacular results. This gets us back to that live
Speaker 1: action and animation discussion. That would be Petro Vlajos, who
Speaker 1: was the engineer who worked on a little film called
Speaker 1: Mary Poppins in the early nineteen sixties. Vlahos wanted to
Speaker 1: improve upon the technology that Butler had created, and one
Speaker 1: of the issues he sought to address was that the
Speaker 1: color blue used for blue screens wasn't a specific wavelength
Speaker 1: of light. You got to remember that the wavelength of light,
Speaker 1: or if you prefer the frequency of light, the two
Speaker 1: are related, determines the light's color, the color that we perceive,
Speaker 1: and the wavelengths corresponding to The blue screens of the
Speaker 1: day ranged from four hundred and thirty five nanometers to
Speaker 1: five hundred nanometers, and that meant any color blue that
Speaker 1: fell in or near that range was off limits for
Speaker 1: use in a scene. Vlajos figured there had to be
Speaker 1: a better way, and he decided to use a different
Speaker 1: backdrop color entirely yellow, but not just any yellow. He
Speaker 1: wanted a precise yellow, the yellow that comes from sodium
Speaker 1: gas discharge lamps. When you excite sodium gas, essentially when
Speaker 1: you energize it with electricity, the gas gives off a
Speaker 1: distinct yellow light with a wavelength of five hundred eighty
Speaker 1: nine nanometers. As long as nothing in the camera frame
Speaker 1: matches that precise shade of yellow, you could have all
Speaker 1: sorts of colors in the shot, including different shades of yellow,
Speaker 1: and not have to worry about skimping on things like
Speaker 1: blue costume pieces. Paired with this was a customized camera
Speaker 1: that contained a prism that could isolate the five hundred
Speaker 1: and eighty nine wavelength of light. Vlahos was able to
Speaker 1: 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 Vlahos only had
Speaker 1: one working prism that could isolate this specific band of light,
Speaker 1: this five hundred and eighty nine nanometer band of light,
Speaker 1: so 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 because came a reality. But first
Speaker 1: let's take another quick break. I've stuck with the film
Speaker 1: world for this podcast so far, but i also have
Speaker 1: to talk about the use of chroma key technology in
Speaker 1: the world of live television. See Mary Poppins came out
Speaker 1: in nineteen sixty four, but the first use of chroma
Speaker 1: key on live TV was in the late nineteen fifties.
Speaker 1: This is the same technology that would become the basis
Speaker 1: for TV weather reports, where the meteorologist stands in front
Speaker 1: of a wall which seems to have a dynamic map
Speaker 1: on 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 chroma key and tested it
Speaker 1: out in nineteen fifty seven with a live broadcast of
Speaker 1: Matinee Theater. The specific story they chose to serve as
Speaker 1: the first experiment here was an adaptation of The Invisible Man,
Speaker 1: and that was fitting because the nineteen thirty three film
Speaker 1: adaptation of The Invisible Man had relied heavily on the
Speaker 1: old Williams process. The live television version initially relied on
Speaker 1: two cameras. One camera would capture a background image, the
Speaker 1: other camera would be the four ground camera that would
Speaker 1: be for all the action in the sequence, and behind
Speaker 1: all this action would be a blue backdrop. Combining these
Speaker 1: two sets of images simultaneously in a device called a
Speaker 1: chroma key amplifier would create a live composite video. Feed.
Speaker 1: Engineers at RCA created the actual technology, and I think
Speaker 1: it's best if I just quote directly from the nineteen
Speaker 1: fifty eight edition of the journal Electronic Ada that describes
Speaker 1: this process. So here's a quote. A switching signal or
Speaker 1: a color key used in association with the special effects amplifier,
Speaker 1: controls the signals sent out over the air. The switching
Speaker 1: signal is in turn created by the camera photographing the
Speaker 1: live action in front of the blue screen. While the
Speaker 1: camera is scanning the blue screen, the switching device automatically
Speaker 1: activates the second camera, which projects the background. When the
Speaker 1: scanning signal reaches an area covered by the live actors,
Speaker 1: the switching device turns off the camera projecting the background
Speaker 1: material and transmits the action. Now that's the end of
Speaker 1: that quote. You could also feed images directly to the
Speaker 1: chroma key amplifier. It didn't have to be a live
Speaker 1: video from a second camera, so you could provide an
Speaker 1: image like a map, allowing a meteorologist to stand in
Speaker 1: front of it otherwise blank blue or green screen and
Speaker 1: gesture at various regions. The audience at home would see
Speaker 1: the meteorologist appearing to stand in front of the map,
Speaker 1: or may be a summary of the forecasted whether for
Speaker 1: the week, and not just a blue screen or a
Speaker 1: green screen. Around the nineteen seventies, that's when we started
Speaker 1: to see a gradual shift, particularly in television, from blue
Speaker 1: screens to green ones. Part of that was because of
Speaker 1: a very slow transition into digital technology. It would become
Speaker 1: more important as digital cameras became a thing. Digital cameras
Speaker 1: were better attuned to doing this with greens rather than
Speaker 1: with blues, although you can do either. But another big
Speaker 1: reason was just that people don't tend to wear a
Speaker 1: lot of green, whereas blue was a pretty and still
Speaker 1: is a pretty popular color. And once in a while
Speaker 1: someone on camera would forget that they're wearing blue, and
Speaker 1: then they'd step in front of a blue screen and
Speaker 1: suddenly their jacket or their shirt or their tie or
Speaker 1: whatever would become part of the background image. Back to
Speaker 1: film for a moment, we're gonna leave TV for a second.
Speaker 1: In nineteen eighty a guy named Richard Edlund, who worked
Speaker 1: on a little film called The Umpire Strikes Back, made
Speaker 1: another big contribution to the chroma key process Edluin developed
Speaker 1: a quad optical printer which both sped up the process
Speaker 1: for producing composite film shots and also brought the price
Speaker 1: 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 them 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 a piece of equipment,
Speaker 1: then do it again and then again and again until
Speaker 1: you finally got whatever result you were after. Gradually, software
Speaker 1: would creep into the realm of film and video effects,
Speaker 1: and this leads us to a version of chroma key
Speaker 1: that I think is actually the easiest to understand. It's
Speaker 1: technically advanced, but the principle is simple. So let's say
Speaker 1: that you want to do a Twitch stream and you're
Speaker 1: playing a video game live, and you want your viewers
Speaker 1: to see you sitting in front of the video game footage.
Speaker 1: So once to make a dynamic background, a video gameplay
Speaker 1: behind you. So you go out and you buy a
Speaker 1: green screen and you set it up behind your gaming chair.
Speaker 1: You throw up some lights more on that in the second,
Speaker 1: and you launch a program that will insert your video
Speaker 1: game capture as a custom digital background. Your viewers will
Speaker 1: see you sitting in front of a screen otherwise filled
Speaker 1: with I don't know, Skyrim or Minecraft or the untitled
Speaker 1: Goose game or whatever it is you're playing. What's going
Speaker 1: on on a technical level, Well, the digital world is
Speaker 1: different from the analog world in lots of ways, but
Speaker 1: importantly for our discussion, it comes down to how in
Speaker 1: the digital world everything ultimately boils down to numeric values.
Speaker 1: You or I could have a debate about whether a
Speaker 1: particular color is aquamarine versus arrow blue, versus blue green
Speaker 1: versus dark cyan, or whatever it may be. But in
Speaker 1: the digital world, every color ultimately has a numeric value.
Speaker 1: Assuming whatever we're looking at is a solid color, you
Speaker 1: could designate that solid color with a specific numeric value
Speaker 1: in computer software and then replicate it or immediately identify
Speaker 1: it within any scene you might see where I'm going here.
Speaker 1: With video software, you can designate a specific color from
Speaker 1: one video source. This specific color is the chroma, as
Speaker 1: it were, and this is the color you want to
Speaker 1: replace or key Outdo software analyzes information that's coming from
Speaker 1: say a digital camera feed into your computer, and it
Speaker 1: looks for any signals that map to the value or
Speaker 1: values of the color or colors you've picked. Most software
Speaker 1: lets you fine tune this, so you can adjust the
Speaker 1: settings to hone in on the specific shade of green
Speaker 1: or blue or whatever it is that you plan to
Speaker 1: key out. Anything that matches that value or range of
Speaker 1: values then gets turned into a transparent video layer. The
Speaker 1: secondary image in our case, the video game footage that
Speaker 1: we're creating as we're playing this game shows through this
Speaker 1: transparent layer, and you can actually think of the foreground
Speaker 1: video as an overlay on top of the digital background
Speaker 1: layer the video game footage. Anything transparent in that overlay
Speaker 1: will show the background through the solid stuff presumably you,
Speaker 1: the Twitch player will block the background image so viewers
Speaker 1: will be able to see their favorite Twitch streamer sitting
Speaker 1: in front of a video game. The software does all
Speaker 1: the work for you, creating the composite video feed that
Speaker 1: the viewer sees. That software, by the way, isn't Twitch itself.
Speaker 1: Twitch is a video streaming platform, but to actually do
Speaker 1: these sort of effects, you'd need to use some other
Speaker 1: piece of software, such as some version of open broadcaster
Speaker 1: software or OBS. And there are a lot of different
Speaker 1: versions of video broadcasting software available for folks to play with,
Speaker 1: from free stuff to professional grade stuff. This type of
Speaker 1: versatility is the kind of stuff that previously you would
Speaker 1: have had to have worked in like a TV studio
Speaker 1: to have access to, but now anyone with a sufficiently
Speaker 1: beefy computer can run this kind of operation. For this
Speaker 1: to work well, you'd want to have really good lighting,
Speaker 1: both for the foreground and for the background drop. You
Speaker 1: want the lighting on the green screen you're using to
Speaker 1: be nice and even, and you want to eliminate any
Speaker 1: chef because if you're casting a shadow on the green screen,
Speaker 1: the camera will pick up that part of the green
Speaker 1: screen as being a darker color and it might even
Speaker 1: be dark enough that the video software doesn't identify it
Speaker 1: as the color that you want to key out, So
Speaker 1: in those cases you would get these weird video artifacts
Speaker 1: on screen. As a result, it'd be really distracting. So
Speaker 1: ideally you want lights that illuminate the green screen evenly
Speaker 1: and are dedicated just for that purpose. If you're lighting
Speaker 1: yourself directly from the front, you're not using a ring
Speaker 1: light or anything like that, then you're going to be
Speaker 1: casting a shadow behind you, unless your Peter Pan, in
Speaker 1: which case I guess you just think happy thoughts. Now,
Speaker 1: this flies for stuff like Zoom meetings and Twitch streams,
Speaker 1: but when it comes to professional grade film, it's not
Speaker 1: really up to snuff. Software can do a bulk of
Speaker 1: the work, but good old human effects artists are still
Speaker 1: needed to make sure everything is coming out well. They
Speaker 1: can step in and do some quality control, can tweak
Speaker 1: things that can fix any issues that pop up, and
Speaker 1: that pays off. You've probably seen a movie that had
Speaker 1: phenomenal attention to this process and the effects are top notch,
Speaker 1: and you've probably seen other movies where, due to whatever reason,
Speaker 1: maybe it was budget, maybe it was just the talent
Speaker 1: of the people working on it, you could tell that
Speaker 1: such care wasn't given to the process, and it shows
Speaker 1: in the final product. I still think films like Jurassic
Speaker 1: Park I'm talking about the original Jurassic Park hold up
Speaker 1: pretty darn well. And part of that is that the
Speaker 1: movie depended on a mixture of different effects. Some of
Speaker 1: them were computer generated and keyed in, some were robotic effects.
Speaker 1: But a lot of this has to do with the
Speaker 1: fact that the effects team as a whole took tremendous
Speaker 1: care 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 going to be
Speaker 1: a lot of other topics are around this that I
Speaker 1: can go into. I could probably talk even more about
Speaker 1: optical printers, for example, and the various approaches to film processing.
Speaker 1: And you can see that while the actual chroma key
Speaker 1: process is very different between film and digital video, the
Speaker 1: basic idea of replacing one color or one element in
Speaker 1: a shot with something from a totally different source remains
Speaker 1: the same. It's the same underlying principle. No matter what
Speaker 1: the actual process is. Yeah, yeah, this this screen bean
Speaker 1: cast role is tight, y'all. Oh my god, mashed potatoes?
Speaker 1: Who invented mashed potatoes? That give that person all the
Speaker 1: Nobel prizes? Okay, that's it for the classic episode tech
Speaker 1: Stuff in front of the grade screen. I hope you're
Speaker 1: having as filling a Thanksgiving as I am. It's great,
Speaker 1: very thankful for you, every one of you. I'm gonna
Speaker 1: go take a nap, and next week we'll be back
Speaker 1: with all new episodes. That should be very well rested
Speaker 1: because I planned to sleep for about eighteen hours. Take care,
Speaker 1: and I'll talk to you again really soon. Tech Stuff
Speaker 1: is an iHeartRadio production. For more podcasts from iHeartRadio, visit
Speaker 1: the iHeartRadio app, Apple Podcasts, or wherever you listen to
Speaker 1: your favorite shows.