WEBVTT - TechStuff In Front of a Green Screen 0:00:04.400 --> 0:00:07.760 Welcome to tex Stuff, a production from I Heart Radio. 0:00:12.200 --> 0:00:15.160 Hey there, and welcome to tech Stuff. I am your host, 0:00:15.320 --> 0:00:18.840 Jonathan Strickland. I'm an executive producer at I Heart Radio 0:00:18.920 --> 0:00:23.600 and I love all things tech. And today's topic goes 0:00:23.720 --> 0:00:29.040 by many names like chroma key, or blue screen or 0:00:29.160 --> 0:00:34.040 green screen. The inventor of this technology developed it for film, 0:00:34.159 --> 0:00:39.400 and that pun was an intentional you know, developed for film, 0:00:39.440 --> 0:00:43.120 But I'm gonna I'm gonna run with it. Today we 0:00:43.600 --> 0:00:48.240 use this technology and film in television, on Twitch streams 0:00:48.280 --> 0:00:50.879 and zoom calls, I mean all over the place. And 0:00:50.920 --> 0:00:53.640 in the old days, you weren't likely to encounter a 0:00:53.720 --> 0:00:58.360 green screen unless you were inside a movie studio, like 0:00:58.800 --> 0:01:01.639 inside a sound stage. But today there are a lot 0:01:01.680 --> 0:01:04.000 of folks who have a green screen just stashed in 0:01:04.040 --> 0:01:07.880 their home office. So today I want to cover this technology, 0:01:07.920 --> 0:01:11.680 it's history and development and how it works. Now, before 0:01:11.720 --> 0:01:14.679 I get into the history, which, as I'm sure most 0:01:14.680 --> 0:01:17.840 of you know, is my moodus up a ran dai, 0:01:18.640 --> 0:01:22.520 let's give a quick overview of what this technology actually does. 0:01:22.680 --> 0:01:26.399 So basically, it's a system that allows a creator to 0:01:26.760 --> 0:01:31.720 insert images, typically a background. That's your standard use of 0:01:31.760 --> 0:01:34.759 this and you do it into a shot that otherwise 0:01:35.400 --> 0:01:38.640 isn't actually in that location, so it could be a 0:01:38.640 --> 0:01:42.160 static image, or the new image might be in motion itself, 0:01:42.200 --> 0:01:45.119 so it might be video or film. This technology allows 0:01:45.160 --> 0:01:48.000 creators to shoot in locations they might otherwise have trouble 0:01:48.080 --> 0:01:50.920 getting to, like the bottom of the ocean, or in 0:01:51.000 --> 0:01:54.840 outer space, or in my old college dorm room because 0:01:54.880 --> 0:01:57.520 I was notorious for locking myself out. So when you 0:01:57.560 --> 0:02:01.400 do it well, it really enhances us scene. But when 0:02:01.440 --> 0:02:05.720 done poorly, it's incredibly distracting because it's so obvious that 0:02:05.760 --> 0:02:08.280 the people or you know whatever that are in the 0:02:08.360 --> 0:02:11.760 foreground of the shot aren't actually in whatever the environment is. 0:02:11.800 --> 0:02:16.200 But that's the basic idea. It's to create a composite, 0:02:16.680 --> 0:02:21.359 a combination of multiple shots into a single new shot, 0:02:22.000 --> 0:02:26.440 so that the components from those two separate shots are 0:02:26.960 --> 0:02:29.320 combined as if they're in the same place at the 0:02:29.360 --> 0:02:32.680 same time. That's the basic idea. Now let's get to 0:02:32.760 --> 0:02:35.880 the history, you know, the part that everyone really came 0:02:35.880 --> 0:02:39.600 here for. But before we even get into the development 0:02:39.639 --> 0:02:42.000 of it, we need to think about the early days 0:02:42.040 --> 0:02:45.760 of film and talk about what film really is, because 0:02:45.800 --> 0:02:47.880 that's going to help us understand the evolution of the 0:02:48.000 --> 0:02:52.119 art form that made chroma key even a possibility. When 0:02:52.120 --> 0:02:56.079 I say film in this case, I'm specifically referencing images 0:02:56.240 --> 0:02:59.720 shot on a long strip of plastic upon which there 0:02:59.800 --> 0:03:03.640 is a coding of light sensitive chemicals. Actually, there are 0:03:03.680 --> 0:03:07.640 several layers of light sensitive particles in that thin strip 0:03:07.720 --> 0:03:10.280 of film. You know, with modern film, you might be 0:03:10.320 --> 0:03:14.240 talking about twenty or more layers on that thin little 0:03:14.240 --> 0:03:17.800 piece of plastic. These layers include binding agents, you know, 0:03:18.040 --> 0:03:22.919 essentially gelatin, and grains of silver halide crystals which react 0:03:22.960 --> 0:03:26.600 to the light. These are those photosensitive chemicals, and also 0:03:26.680 --> 0:03:29.920 some special molecules that bind with silver halide crystal so 0:03:29.960 --> 0:03:33.919 that they transfer energy from specific wavelengths of light, which 0:03:34.240 --> 0:03:38.840 we perceive as different colors. When light hits the silver 0:03:38.960 --> 0:03:43.360 halide crystals coding this plastic, there is a chemical reaction, 0:03:43.600 --> 0:03:46.160 and you can think of it as a chemical record 0:03:46.560 --> 0:03:50.360 of that instant of time. Whatever light hit the film 0:03:50.440 --> 0:03:54.360 is recorded there on this piece of plastics. So if 0:03:54.360 --> 0:03:57.800 you position the lenses so that you can direct specific 0:03:57.960 --> 0:04:01.480 light to that film, you can take a photograph. You 0:04:01.560 --> 0:04:04.640 must use some form of shutter to block out the 0:04:04.760 --> 0:04:07.520 light until you're ready to take your image. Then you 0:04:07.640 --> 0:04:11.160 open the shutter. This exposes that piece of film to 0:04:11.240 --> 0:04:14.000 the light that's being reflected off of whatever it is 0:04:14.040 --> 0:04:17.599 your photographing. Remember when we see things, we're seeing light 0:04:17.800 --> 0:04:21.039 bouncing off of that and the color of the stuff 0:04:21.080 --> 0:04:26.159 we see is dependent upon which frequencies of light bounce 0:04:26.279 --> 0:04:30.120 off of that thing. So then the shutter closes on 0:04:30.160 --> 0:04:33.000 your camera and you've got your chemical record. And the 0:04:33.040 --> 0:04:36.600 shutter is necessary because, as I said, these chemicals react 0:04:36.600 --> 0:04:39.240 to light. If you just had this stuff exposed to 0:04:39.320 --> 0:04:42.320 light all the time, it would have already reacted. You 0:04:42.320 --> 0:04:43.880 would not be able to use it to take a 0:04:43.920 --> 0:04:46.839 photograph of anything. If you want to learn more about 0:04:46.880 --> 0:04:51.000 this process, which is fascinating, but really the process of 0:04:51.000 --> 0:04:53.240 photography is far enough out of the scope of this 0:04:53.279 --> 0:04:56.200 episode that I don't want to go into it much further. 0:04:56.680 --> 0:05:00.440 I do recommend you go to how Stuff Works dot Calm. 0:05:00.480 --> 0:05:03.880 That's my old employer. I don't technically work for How 0:05:03.920 --> 0:05:07.240 Stuff Works anymore, but you can go to that website 0:05:07.360 --> 0:05:10.760 and you look at the article how Photographic Film Works. 0:05:11.080 --> 0:05:13.760 It was written by Chuck Woodworth and it's a great 0:05:13.880 --> 0:05:16.839 example of the health Stuff Work style, and it goes 0:05:16.839 --> 0:05:20.720 into the chemistry and physics of the photographic process, but 0:05:21.000 --> 0:05:23.279 we'll skim over the rest of that for the purposes 0:05:23.320 --> 0:05:26.640 of this episode. So, now the film on the camera 0:05:26.760 --> 0:05:30.159 has a latent image on it, and it represents the 0:05:30.279 --> 0:05:33.880 moment in time the shutter allowed light to pass from 0:05:33.920 --> 0:05:37.080 the lens to hit the film. But in a film 0:05:37.200 --> 0:05:40.960 camera a cinema camera, you're talking about a series of 0:05:41.080 --> 0:05:45.960 latent images. Motors pull this strip of film at a 0:05:46.040 --> 0:05:50.000 steady speed through the frame of the camera where the 0:05:50.000 --> 0:05:54.600 shutter opens and closes at a regular uh frequency. And 0:05:54.640 --> 0:06:00.120 the standard speed of capturing images is twenty four frames 0:06:00.200 --> 0:06:04.000 per second, so a film camera is capturing twenty four 0:06:04.160 --> 0:06:08.480 photographs every second. The latent images needs some processing in 0:06:08.560 --> 0:06:10.800 order to create something that can be fed through a 0:06:10.839 --> 0:06:14.279 film projector. The development process creates a negative image of 0:06:14.279 --> 0:06:18.240 the chemical record, and that means that the darkest areas 0:06:18.279 --> 0:06:21.120 of the image represent the spots where the film received 0:06:21.120 --> 0:06:24.919 the most light. It's the opposite of what you would expect, 0:06:25.000 --> 0:06:28.080 right Anything that would be dark in a photograph will 0:06:28.120 --> 0:06:31.359 be light on a negative and vice versa. This negative 0:06:31.400 --> 0:06:33.599 has to be transferred onto another roll of film to 0:06:33.600 --> 0:06:36.080 create a positive image. In a process that I'm also 0:06:36.120 --> 0:06:37.719 not going to cover because we need some time for 0:06:37.760 --> 0:06:41.159 actual topic. Right. So, when we watch a film, we 0:06:41.279 --> 0:06:45.080 have the perception that what we're viewing are moving objects 0:06:45.200 --> 0:06:48.640 up on a screen, but that is an illusion. What 0:06:48.800 --> 0:06:52.040 we're really seeing with true film is that it's a 0:06:52.080 --> 0:06:55.760 series of photographs. The projector is playing those photographs at 0:06:55.800 --> 0:06:58.039 the same speed that the film camera used to make 0:06:58.080 --> 0:07:02.680 them twenty four frames per second usually. I mean, if 0:07:02.720 --> 0:07:04.960 you wanted to play stuff in slow motion, then you 0:07:04.960 --> 0:07:07.120 would shoot a film at a much higher frame rate, 0:07:07.160 --> 0:07:10.360 like forty eight frames per second, but you would play 0:07:10.360 --> 0:07:13.560 it back at the standard twenty four frames per second, 0:07:13.800 --> 0:07:17.760 and that would give you the slow motion effect. And 0:07:17.800 --> 0:07:21.160 back in the old days, cameras were hand cranked, so 0:07:21.680 --> 0:07:25.120 you would get kind of twenty four frames per second, 0:07:25.600 --> 0:07:28.360 but this would result in sort of that herky jerky 0:07:28.440 --> 0:07:33.880 movement we associate with old movies that was hand cranked cinematography, 0:07:33.960 --> 0:07:38.040 and sometimes people would turn the crank a little faster 0:07:38.160 --> 0:07:40.560 or a little slower than others, so you don't really 0:07:40.560 --> 0:07:44.760 have a consistent experience there, because the playback speed, especially 0:07:44.800 --> 0:07:47.760 if you're playing it in a modern projector, is going 0:07:47.800 --> 0:07:51.400 to be standard, even if the recording speed wasn't. But 0:07:51.520 --> 0:07:53.680 never mind all that. If you were to stop the 0:07:53.720 --> 0:07:57.480 projectors reels at any given moment in the playback of 0:07:57.520 --> 0:08:00.720 a film, you would see a still m page. You 0:08:00.720 --> 0:08:03.320 would advance the reel by one frame, and you would 0:08:03.320 --> 0:08:06.920 see the next image in the next photograph in that series, 0:08:07.200 --> 0:08:09.240 and you would likely be able to pick out how 0:08:09.280 --> 0:08:12.440 things are slightly different from the first frame you looked 0:08:12.440 --> 0:08:15.160 at and the next frame. And this is the same 0:08:15.200 --> 0:08:18.080 principle that's behind animation. If you've ever taken a pad 0:08:18.120 --> 0:08:21.800 of sticky notes and you drawn little figures on page 0:08:21.800 --> 0:08:23.680 after page after page, so that when you flip the 0:08:23.720 --> 0:08:26.960 pages you get a simple little cartoon, then you've engaged 0:08:27.000 --> 0:08:30.080 in the same art form as great cinematographers. Then maybe 0:08:30.080 --> 0:08:32.280 your work was even better than theirs. I'm not one 0:08:32.360 --> 0:08:34.520 to judge. Now, why would I go to the trouble 0:08:34.600 --> 0:08:36.920 to cover the basics of film, Well, it's because the 0:08:37.000 --> 0:08:40.800 very nature of film inspired certain people to experiment with it, 0:08:40.840 --> 0:08:43.760 to try stuff that would be impossible to replicate in 0:08:43.760 --> 0:08:46.440 a real world setting, or at least it would be 0:08:46.960 --> 0:08:51.800 really difficult. Film wasn't a substitution for theater in theater, 0:08:51.920 --> 0:08:55.199 you can create a few interesting effects. Generally your options 0:08:55.200 --> 0:08:59.320 are limited to things like lighting tricks. Maybe some creative 0:08:59.360 --> 0:09:03.040 sets are called costumes, maybe an even a stage illusion 0:09:03.200 --> 0:09:06.359 or two, and perhaps some sound design. But with film 0:09:06.400 --> 0:09:10.079 there were other possibilities, and one fellow who recognized those 0:09:10.120 --> 0:09:16.319 possibilities was the French filmmaker and illusionist George Meillier. He 0:09:16.360 --> 0:09:19.960 was born in Paris. You know Paris in eighteen sixty one. 0:09:20.400 --> 0:09:23.000 Let that sink in for a moment. This man was 0:09:23.200 --> 0:09:26.400 born while the Civil War was going on in the 0:09:26.480 --> 0:09:30.960 United States. He became interested in stagecraft and magic, and 0:09:31.000 --> 0:09:34.440 by the eighteen nineties he was a successful stage magician. 0:09:34.960 --> 0:09:38.480 In eight he saw an early film exhibition made by 0:09:38.480 --> 0:09:42.760 the Lumier Brothers and he became entranced by this new medium. 0:09:42.840 --> 0:09:45.960 His experience and illusions encouraged him to find ways to 0:09:46.040 --> 0:09:49.880 experiment with film to achieve new effects, stuff that wouldn't 0:09:49.920 --> 0:09:52.959 be possible to do in the real world. He was 0:09:53.000 --> 0:09:56.400 a special effects and film pioneer. He established methods to 0:09:56.440 --> 0:10:01.560 shoot slow motion, stop motion animation, to dissolves, and tricks 0:10:01.600 --> 0:10:07.240 like super imposition and double exposure around. Maillier had a 0:10:07.280 --> 0:10:10.200 really cool idea. He wanted to create a truly bizarre 0:10:10.240 --> 0:10:13.160 special effect in which an actor would appear to remove 0:10:13.280 --> 0:10:18.760 his own head on screen. But how would he accomplish this, Well, 0:10:18.800 --> 0:10:22.480 the secret was in shooting multiple exposures of the same 0:10:22.600 --> 0:10:26.120 reel of film. Typically, after you expose film to light, 0:10:26.200 --> 0:10:28.959 you want to avoid doing that again because you will 0:10:29.000 --> 0:10:31.480 interfere with that chemical record. You know, if you were 0:10:31.480 --> 0:10:34.800 to ever take photographs with a film camera and then 0:10:34.920 --> 0:10:37.640 someone were to open up the back of the camera 0:10:37.640 --> 0:10:43.000 and expose the film to regular light, you could potentially 0:10:43.080 --> 0:10:45.680 ruin shots that were already made, plus ruin the film 0:10:45.720 --> 0:10:48.760 for the next couple of shots. It's not something that 0:10:48.840 --> 0:10:52.160 you typically want to do. More light will cause further 0:10:52.240 --> 0:10:56.520 reactions chemical reactions on the actual plastic film, and your 0:10:56.520 --> 0:10:59.800 shot gets ruined. If you've ever used the cameras that 0:11:00.240 --> 0:11:02.800 quite line up the film properly at the very beginning 0:11:02.800 --> 0:11:04.760 of the very end, you might even notice that a 0:11:04.800 --> 0:11:09.160 couple of photos on those sections of the film role 0:11:09.640 --> 0:11:13.240 have two sets of images superimposed on top of one another, 0:11:14.000 --> 0:11:17.200 and that's because that little section of film was exposed 0:11:17.240 --> 0:11:21.679 more than once. Mellier did this on purpose. He would 0:11:21.720 --> 0:11:24.360 set up a shot and he would use a lens 0:11:24.440 --> 0:11:27.559 that had some of the lens blacked out so that 0:11:27.640 --> 0:11:30.360 light could not pass through that part of the lens. 0:11:30.760 --> 0:11:33.840 And we refer to this as a MAT M A 0:11:34.120 --> 0:11:36.240 T T E. And you can think of it like 0:11:36.280 --> 0:11:39.200 a mask for the lens, and that would mean a 0:11:39.240 --> 0:11:41.839 section of each frame corresponding to that part of the 0:11:41.880 --> 0:11:44.719 mat would remain unexposed to light. He would shoot the 0:11:44.880 --> 0:11:49.120 scene as rehearsed. Afterward, he would rewind the exposed film 0:11:49.160 --> 0:11:51.200 in the camera, beat it right back in as if 0:11:51.200 --> 0:11:53.640 he was going to shoot something all for the first time. 0:11:54.480 --> 0:11:58.360 And he would then replace this mat with a new one, 0:11:58.880 --> 0:12:02.119 and the new man at would block out everything except 0:12:02.840 --> 0:12:07.199 the section that previously was unexposed, So, in other words, 0:12:07.400 --> 0:12:10.160 the part that was black would now be clear and 0:12:10.200 --> 0:12:13.960 the rest of the lens that was previously unblacked would 0:12:14.000 --> 0:12:16.920 be blacked. So you replace one mat with a different one, 0:12:17.640 --> 0:12:20.400 so he would then be able to film something totally 0:12:20.400 --> 0:12:22.720 new into this same role of film, and this time 0:12:22.800 --> 0:12:25.480 the camera would pick up a new scene, and by 0:12:25.559 --> 0:12:27.760 changing things between one section and the other, he could 0:12:27.800 --> 0:12:31.120 create weird effects like the head removal trick. It would 0:12:31.120 --> 0:12:33.680 appear as though all of this was shot at the 0:12:33.720 --> 0:12:36.600 same time on the same role of film, but in fact, 0:12:37.000 --> 0:12:39.800 through careful control of where the light would go, Millier 0:12:39.960 --> 0:12:44.440 would use the same film twice or more to produce 0:12:44.480 --> 0:12:46.880 cool results. And if you want to see an example 0:12:46.920 --> 0:12:50.000 of what I'm talking about, and I highly recommend you 0:12:50.080 --> 0:12:53.440 check this out because it is amazing even today, go 0:12:53.600 --> 0:12:56.440 to YouTube and do a search for the short film 0:12:56.920 --> 0:13:01.000 four Heads are better than One. The activity of this film, 0:13:01.000 --> 0:13:04.560 which by the way, lasts less than a minute, is 0:13:04.600 --> 0:13:09.920 still astonishing. To say his experimental work was influential would 0:13:09.960 --> 0:13:13.520 be a gross understatement. Other filmmakers inspired by the work 0:13:13.520 --> 0:13:17.599 of Mailier tried new techniques that built upon the foundation 0:13:17.640 --> 0:13:22.360 he established. For example, filmmaker and documentary and Norman Down 0:13:22.600 --> 0:13:26.680 wanted to shoot films at historic buildings around California, but 0:13:27.200 --> 0:13:31.240 several of those buildings had been damaged or even partly destroyed. 0:13:31.840 --> 0:13:35.920 Other historic buildings had modern stuff like light poles in 0:13:35.960 --> 0:13:37.920 front of them. He didn't want that to be in 0:13:37.920 --> 0:13:40.600 the shot, so he wanted to show the buildings as 0:13:40.640 --> 0:13:44.480 they had appeared in their original form before the decay, 0:13:44.679 --> 0:13:49.560 before modern technology had advanced into the area. So he 0:13:49.679 --> 0:13:53.719 came up with a really clever idea. Dawn placed a 0:13:53.800 --> 0:13:57.200 pain of glass between the camera and the scene he 0:13:57.280 --> 0:14:00.640 wanted to shoot, and on that pain of ass he 0:14:00.720 --> 0:14:04.600 had paintings to enhance the scene. If a building's roof 0:14:04.640 --> 0:14:06.880 had caved in, he would frame up the shot and 0:14:06.880 --> 0:14:09.440 then have an artist paint a roof on the glass 0:14:09.600 --> 0:14:12.600 so that when viewed through the camera, the painting and 0:14:12.640 --> 0:14:15.600 the building behind it would line up and the building 0:14:15.600 --> 0:14:18.160 would appear to be whole again. Or he might want 0:14:18.160 --> 0:14:20.880 to cover up stuff like those telephone poles, he would 0:14:20.880 --> 0:14:24.040 have an artist paint trees on the glass so from 0:14:24.040 --> 0:14:27.880 the camera's perspective the polls were hidden. His process also 0:14:27.920 --> 0:14:32.479 involved double exposures. This was an example of a Matt painting, 0:14:32.880 --> 0:14:35.840 and he would claim credit for inventing this, and he 0:14:35.880 --> 0:14:39.080 even applied for a patent on it, but subsequent lawsuits 0:14:39.160 --> 0:14:42.640 established other filmmakers were using similar approaches, and the patent 0:14:42.640 --> 0:14:46.600 office ultimately denied the claim, but Matt paintings would become 0:14:46.600 --> 0:14:50.160 an important part of filmmaking from that point forward. One 0:14:50.240 --> 0:14:54.200 disadvantage to these early film effects was they required the 0:14:54.280 --> 0:14:57.560 camera to remain stationary that the whole process. You couldn't 0:14:57.680 --> 0:15:01.000 move the camera at all or else your shots wouldn't 0:15:01.040 --> 0:15:03.560 line up, so you wanted the camera to remain in 0:15:03.600 --> 0:15:07.320 one place through all of these different exposures. Another problem 0:15:07.400 --> 0:15:10.400 was that no action could cross the Matt line because 0:15:10.400 --> 0:15:13.480 it would get cut off as it moved beyond that 0:15:13.880 --> 0:15:18.120 invisible at least from the audience's perspective line. Now, let's 0:15:18.160 --> 0:15:20.920 move on up to nine eighteen, when a guy named 0:15:20.960 --> 0:15:26.880 Frank Williams created the Williams process, which honestly seems pretty 0:15:26.920 --> 0:15:31.160 convenient to me. The Williams process allowed for more movement 0:15:31.400 --> 0:15:34.720 and involved shooting actors against a solid background, such as 0:15:34.760 --> 0:15:39.800 a black or blue curtain on very high contrast film. 0:15:39.840 --> 0:15:44.520 The process sometimes required multiple transfers onto new film until 0:15:44.560 --> 0:15:48.840 you arrived at a black silhouette against a pure white background, 0:15:49.000 --> 0:15:51.520 the negative image of what you were shooting before, and 0:15:51.560 --> 0:15:54.280 this was called a holdout matt. The way these transfers 0:15:54.280 --> 0:15:56.640 typically would work is that you would put one strip 0:15:56.840 --> 0:16:00.760 of shot developed film into a camera, so you've already 0:16:00.760 --> 0:16:02.640 shot on it, but you're putting it through the camera again, 0:16:03.520 --> 0:16:08.040 and you would put a second strip of film that 0:16:08.200 --> 0:16:12.320 is unshot, it's unprocessed, no no lights hit it, and 0:16:12.400 --> 0:16:16.480 put it right up against the first developed piece of film, 0:16:16.720 --> 0:16:19.760 you would shine light through the camera and you would 0:16:19.800 --> 0:16:23.280 let it just run, and this way you would transfer 0:16:23.400 --> 0:16:27.760 the images from one strip to the other. And this 0:16:27.880 --> 0:16:30.960 was called by packing because you were putting two different 0:16:31.000 --> 0:16:35.479 pieces of film through the camera to achieve this process. 0:16:35.520 --> 0:16:38.360 And you could also do this not just with developed 0:16:38.360 --> 0:16:40.880 film where you're making copies. You could do it with negatives. 0:16:40.920 --> 0:16:44.400 You could do it in a way to increase contrast 0:16:44.520 --> 0:16:47.240 from copy to copy, until you were able to create 0:16:47.640 --> 0:16:51.760 a holdout matt. Reverse printing the holdout Matt creates a 0:16:51.840 --> 0:16:56.040 white silhouette on a black background or a cover mat. 0:16:56.120 --> 0:16:58.400 So now you've got to hold out Matt and a 0:16:58.440 --> 0:17:01.360 cover matt. You would take the footage of a previously 0:17:01.400 --> 0:17:04.520 shot background. Let's say it's a foreboding forest. So you've 0:17:04.520 --> 0:17:07.240 shot your actors in a sound stage, but you want 0:17:07.240 --> 0:17:10.280 the background to be this really scary looking forest, and 0:17:10.400 --> 0:17:13.040 you would bypack a film and camera with the background 0:17:13.119 --> 0:17:17.160 footage that you had shot and the black silhouette holdout 0:17:17.320 --> 0:17:21.800 Matt of the actor's footage that you shot. Then you 0:17:21.840 --> 0:17:26.400 would transfer this combination to a third piece of unexposed 0:17:26.440 --> 0:17:29.240 film by again shining a light through those other two 0:17:29.240 --> 0:17:33.479 pieces and because the background on the holdout mat is white, 0:17:34.480 --> 0:17:36.840 the light passes through it easily and it hits the 0:17:36.920 --> 0:17:40.520 previously shot background image that comes through and gets copied 0:17:40.520 --> 0:17:44.520 onto the blank film. The silhouette of your actors is 0:17:44.560 --> 0:17:49.080 black that prevents light from passing through. So the previously 0:17:49.160 --> 0:17:52.440 blank third piece of film now has a background image 0:17:52.520 --> 0:17:55.800 and this dark silhouette of actors moving through the frame. 0:17:56.760 --> 0:17:59.600 Then you would have to take that piece of film 0:17:59.640 --> 0:18:02.240 that has this black silhouette and you have to bypack 0:18:02.280 --> 0:18:05.199 it with the original footage of the actor, not the silhouette, 0:18:05.200 --> 0:18:08.760 but the actual actor footage. And now the real actor 0:18:09.000 --> 0:18:11.600 is on top of the silhouette and appears to actually 0:18:11.640 --> 0:18:14.359 be in front of whatever the background images, in our case, 0:18:14.400 --> 0:18:18.360 the foreboding forest. Because this type of matt moves from 0:18:18.440 --> 0:18:22.120 frame to frame, it's called a traveling matt. And if 0:18:22.160 --> 0:18:25.840 you remember Fraggle Rock, you might remember traveling matt is 0:18:25.880 --> 0:18:29.399 the name of go Bo's uncle. Gobo, by the way, 0:18:29.640 --> 0:18:32.320 is another stage in lighting term. It stands for a 0:18:32.359 --> 0:18:35.320 template or stencil that controls the shape of a lamps 0:18:35.359 --> 0:18:41.240 emitted light. So some of the Fraggles had fun industry 0:18:41.359 --> 0:18:44.879 names Gobo and traveling Matt. When we come back, we 0:18:44.960 --> 0:18:49.280 will continue down the history of how chroma key came about, 0:18:49.359 --> 0:18:59.160 but first let's take a quick break. Before the break, 0:18:59.240 --> 0:19:02.800 I was talking up the Williams process, but see Dodge 0:19:02.880 --> 0:19:06.800 Dunning would improve upon the Williams process by using yellow 0:19:06.840 --> 0:19:09.200 light to shoot the actor in front of a blue screen, 0:19:09.800 --> 0:19:13.760 creating the Dunning process. And this was used extensively in 0:19:13.800 --> 0:19:17.359 the classic nineteen thirty three film King Kong, and they 0:19:17.359 --> 0:19:19.639 weren't great for black and white film. Remember this is 0:19:19.680 --> 0:19:23.640 before anyone was shooting on color. So although I mean 0:19:23.640 --> 0:19:26.600 there were ways of treating film to create color, but 0:19:26.720 --> 0:19:29.440 this was standard black and white film, so he didn't 0:19:29.440 --> 0:19:32.560 have to worry about the weird lighting. But if you 0:19:32.560 --> 0:19:35.760 wanted to shoot in color, that was gonna cause require 0:19:35.840 --> 0:19:41.080 other considerations. Around the same time, engineers were developing the 0:19:41.160 --> 0:19:45.360 optical printer, which really simplified the process of transferring images 0:19:45.400 --> 0:19:47.720 from one strip of film to another. And I had 0:19:47.720 --> 0:19:52.639 talked about by packing, but the optical process could be 0:19:53.080 --> 0:19:56.399 an alternative to that. It didn't eliminate it, but it 0:19:56.480 --> 0:19:59.240 was a different way to achieve the same thing. Essentially, 0:20:00.000 --> 0:20:03.720 an optical printer has a projector on one side and 0:20:03.760 --> 0:20:06.840 a camera. On the other the projector shoots at the 0:20:06.880 --> 0:20:10.160 projected image that then gets copied onto a new unexposed 0:20:10.240 --> 0:20:12.639 role of film inside the camera. And it also allowed 0:20:12.640 --> 0:20:15.680 filmmakers to create new effects by changing the focal point 0:20:15.920 --> 0:20:18.639 of the camera or the distance between the projector and 0:20:18.680 --> 0:20:21.840 the camera, and rather than bypacking camera, you just use 0:20:21.920 --> 0:20:25.440 this process you could get better results. The first mass 0:20:25.480 --> 0:20:28.200 produced optical printer hit the market in the mid nineteen 0:20:28.280 --> 0:20:32.240 forties came from a company called Acme Done. In addition, 0:20:32.359 --> 0:20:37.200 filmmakers created rear projection background so in these actors would 0:20:37.240 --> 0:20:41.040 perform in front of a screen like a projection screen, 0:20:41.240 --> 0:20:44.800 not a green screen or a blue screen, and behind 0:20:45.160 --> 0:20:48.400 that screen would be a film projector and it would 0:20:48.400 --> 0:20:52.879 provide a projected background image. You could do this in 0:20:52.960 --> 0:20:56.359 place of the processes have already described, putting your actors 0:20:56.400 --> 0:20:58.679 in front of a screen that shows whatever background you 0:20:58.720 --> 0:21:01.560 wanted in the background could be fairly static, but didn't 0:21:01.640 --> 0:21:04.679 have to be. You could include a background that was 0:21:05.000 --> 0:21:08.359 actually dynamic, showing movement. It could be a film in 0:21:08.440 --> 0:21:11.320 of itself. This was used a lot in shots where 0:21:11.320 --> 0:21:14.639 people were in vehicles and talking with one another, so 0:21:14.760 --> 0:21:17.720 rather than setting up a car on a trailer and 0:21:17.800 --> 0:21:19.679 shooting it in the real world with the camera on 0:21:19.720 --> 0:21:21.800 the trailer, or or worse yet, trying to figure out 0:21:21.840 --> 0:21:24.760 how to fit a camera onto a real moving car 0:21:24.920 --> 0:21:28.160 that's operated by an actor. You would typically have performance 0:21:28.200 --> 0:21:31.800 sitting in a stationary vehicle, and the screen behind and 0:21:31.880 --> 0:21:35.760 sometimes to either side of them would display previously shot 0:21:35.760 --> 0:21:40.080 footage of scenery going by from the correct perspective, as 0:21:40.119 --> 0:21:42.920 if the car were driving down the road. This wasn't 0:21:42.960 --> 0:21:46.399 necessarily convincing, mind you, but it was an interesting technique. 0:21:46.840 --> 0:21:50.639 In ninety two, engineers created a process to produce films 0:21:50.640 --> 0:21:56.400 and color called appropriately Technicolor. Interestingly, in this process, images 0:21:56.480 --> 0:22:00.359 would be captured to three strips of black and white film. 0:22:00.560 --> 0:22:04.000 At this stage is the try strip approach. This was 0:22:04.040 --> 0:22:07.840 not the original version of Technicolor. It was technically the 0:22:07.880 --> 0:22:11.640 fourth incarnation of the Technicolor technology, but it's the important 0:22:11.640 --> 0:22:15.480 one for our discussion. So how do you produce a 0:22:15.560 --> 0:22:19.200 color image if you're using black and white film as 0:22:19.240 --> 0:22:22.560 your medium, Well, first you have to shoot your footage 0:22:22.640 --> 0:22:27.640 and inside an early technic color tri strip camera. Behind 0:22:28.119 --> 0:22:31.760 the lens was an optical cube and it acted as 0:22:31.760 --> 0:22:36.760 a prism prisms break up incoming light into bands of frequencies, 0:22:37.160 --> 0:22:40.639 and you've likely had one, or played with one, or 0:22:40.640 --> 0:22:42.879 at least seen one. That's the kind of stuff, you know. 0:22:42.920 --> 0:22:44.800 The light goes through it and then it makes rainbows. 0:22:44.800 --> 0:22:48.760 You see a little rainbow pattern projected somewhere. This prism 0:22:48.960 --> 0:22:51.919 would break up the incoming light into three general bands 0:22:51.960 --> 0:22:56.040 that corresponded with red, green, and blue. Each of those 0:22:56.080 --> 0:22:59.440 bands of light would hit one of three strips of 0:22:59.480 --> 0:23:02.639 black and white film inside the camera, So one strip 0:23:02.680 --> 0:23:04.840 of film would be exposed to all the red light 0:23:05.000 --> 0:23:07.840 coming from a scene, one from all the green light 0:23:08.000 --> 0:23:10.960 coming from a scene, one from the blue. The concentration 0:23:10.960 --> 0:23:13.360 of each color in the scene would affect how much 0:23:13.440 --> 0:23:16.199 light was hitting each strip of film, so you'd end 0:23:16.280 --> 0:23:19.840 up with three negatives of your scene that we're all 0:23:20.160 --> 0:23:23.800 perfectly synchronized, all of them in black and white, but 0:23:24.200 --> 0:23:28.439 each with different levels of brightness for different objects. It 0:23:28.480 --> 0:23:31.520 all depended on what color the objects were in the scene. 0:23:31.800 --> 0:23:34.920 A red chair, for example, would appear as a very 0:23:34.960 --> 0:23:37.560 prominent image on the black and white film that was 0:23:37.640 --> 0:23:40.640 hit with the red light, while it would be less 0:23:40.680 --> 0:23:45.120 noticeable in the green and blue strips. Now you would 0:23:45.160 --> 0:23:48.240 develop the negatives, and you would process the film, the 0:23:48.359 --> 0:23:51.320