WEBVTT - Rerun: TechStuff In Front of a Green Screen 0:00:04.440 --> 0:00:12.879 Welcome to tech Stuff, a production from iHeartRadio. Hey Thearon, 0:00:13.039 --> 0:00:16.320 Welcome to tech Stuff. I'm your host, Jonathan Strickland. I'm 0:00:16.360 --> 0:00:19.400 an executive producer with iHeart Podcasts. And how the tech 0:00:19.440 --> 0:00:22.080 are you well? Here in the United States, we are 0:00:22.120 --> 0:00:26.479 celebrating Thanksgiving, which means our office is closed, so I 0:00:26.520 --> 0:00:29.440 do not have a brand new episode for you, but 0:00:29.560 --> 0:00:32.440 I do have a pretty cool episode that we published 0:00:32.479 --> 0:00:36.600 on June one, twenty twenty. It is titled tech Stuff 0:00:36.760 --> 0:00:40.720 in front of a Green Screen. So I hope you enjoy. 0:00:40.800 --> 0:00:43.520 And for those of you who are celebrating, Happy Thanksgiving, 0:00:44.440 --> 0:00:46.640 and for those of y'all not in the United States, 0:00:46.960 --> 0:00:50.120 maybe in Canada where you had Thanksgiving already. To you, 0:00:50.240 --> 0:00:55.320 I say happy Thursday, enjoy this rerun episode of tech Stuff. 0:00:58.440 --> 0:01:04.600 Today's topic goes by many names like chroma key, or 0:01:04.720 --> 0:01:09.559 blue screen or green screen. The inventor of this technology 0:01:09.600 --> 0:01:14.600 developed it for film, and that pun was unintentional, you know, 0:01:15.120 --> 0:01:19.640 developed for film, but I'm gonna run with it. Today 0:01:19.800 --> 0:01:25.120 we use this technology in film, in television, on Twitch streams, 0:01:25.160 --> 0:01:27.760 and zoom calls, I mean all over the place. And 0:01:27.800 --> 0:01:30.560 in the old days you weren't likely to encounter a 0:01:30.600 --> 0:01:35.200 green screen unless you were inside a movie studio, like 0:01:35.720 --> 0:01:38.640 inside a soundstage. But today there are a lot of 0:01:38.680 --> 0:01:41.080 folks who have a green screen just stashed in their 0:01:41.120 --> 0:01:44.440 home office. So today I want to cover this technology, 0:01:44.760 --> 0:01:48.560 it's history and development and how it works. Now, before 0:01:48.560 --> 0:01:51.559 I get into the history, which, as I'm sure most 0:01:51.560 --> 0:01:56.280 of you know, is my modus oparandi, let's give a 0:01:56.360 --> 0:02:01.080 quick overview of what this technology actually does. So it's 0:02:01.160 --> 0:02:05.880 a system that allows a creator to insert images, typically 0:02:06.080 --> 0:02:09.760 a background that's your standard use of this, and you 0:02:09.840 --> 0:02:13.200 do it into a shot that otherwise isn't actually in 0:02:13.280 --> 0:02:16.760 that location, so it could be a static image, or 0:02:16.840 --> 0:02:19.239 the new image might be in motion itself, so it 0:02:19.320 --> 0:02:22.560 might be video or film. This technology allows creators to 0:02:22.600 --> 0:02:25.360 shoot in locations they might otherwise have trouble getting to, 0:02:25.639 --> 0:02:28.640 like the bottom of the ocean or an outer space, 0:02:28.800 --> 0:02:32.000 or in my old college dorm room because I was 0:02:32.040 --> 0:02:35.120 notorious for locking myself out. So when you do it well, 0:02:35.520 --> 0:02:39.520 it really enhances a scene. But when done poorly, it's 0:02:39.560 --> 0:02:43.400 incredibly distracting because it's so obvious that the people or 0:02:43.440 --> 0:02:46.040 you know whatever that are in the foreground of the 0:02:46.080 --> 0:02:49.920 shot aren't actually in whatever the environment is. But that's 0:02:49.960 --> 0:02:54.400 the basic idea. It's to create a composite, a combination 0:02:54.760 --> 0:02:59.160 of multiple shots into a single new shot, so that 0:02:59.400 --> 0:03:03.239 the component and it's from those two separate shots are 0:03:03.840 --> 0:03:06.200 combined as if they're in the same place at the 0:03:06.200 --> 0:03:09.520 same time. That's the basic idea. Now let's get to 0:03:09.639 --> 0:03:12.720 the history, you know, the part that everyone really came 0:03:12.760 --> 0:03:16.480 here for. But before we even get into the development 0:03:16.520 --> 0:03:18.880 of it, we need to think about the early days 0:03:18.919 --> 0:03:22.640 of film and talk about what film really is, because 0:03:22.680 --> 0:03:24.720 that's going to help us understand the evolution of the 0:03:24.840 --> 0:03:28.960 art form that made chroma key even a possibility. When 0:03:29.000 --> 0:03:32.959 I say film in this case, I'm specifically referencing images 0:03:33.080 --> 0:03:36.640 shot on a long strip of plastic upon which there 0:03:36.680 --> 0:03:40.520 is a coating of light sensitive chemicals. Actually, there are 0:03:40.560 --> 0:03:44.520 several layers of light sensitive particles in that thin strip 0:03:44.600 --> 0:03:47.160 of film. You know, with modern film you might be 0:03:47.200 --> 0:03:51.080 talking about twenty or more layers on that thin little 0:03:51.080 --> 0:03:54.680 piece of plastic. These layers include binding agents, you know, 0:03:54.920 --> 0:03:59.720 essentially gelatine and grains of silver halid crystals, which react 0:03:59.720 --> 0:04:03.400 to the light. These are those photosensitive chemicals and also 0:04:03.520 --> 0:04:06.800 some special molecules that bind with silver haylid crystal so 0:04:06.840 --> 0:04:10.760 that they transfer energy from specific wavelengths of light, which 0:04:11.080 --> 0:04:15.720 we perceive as different colors. When light hits the silver 0:04:15.800 --> 0:04:20.160 haylight crystals coating this plastic, there is a chemical reaction, 0:04:20.480 --> 0:04:23.039 and you can think of it as a chemical record 0:04:23.400 --> 0:04:26.880 of that instant of time. Whatever light hit the film 0:04:27.279 --> 0:04:31.240 is recorded there on this piece of plastic. So if 0:04:31.240 --> 0:04:34.680 you position the lenses so that you can direct specific 0:04:34.800 --> 0:04:38.359 light to that film, you can take a photograph. You 0:04:38.440 --> 0:04:41.520 must use some form of shutter to block out the 0:04:41.600 --> 0:04:44.200 light until you are ready to take your image. Then 0:04:44.240 --> 0:04:47.840 you open the shutter. This exposes that piece of film 0:04:47.960 --> 0:04:50.760 to the light that's being reflected off of whatever it 0:04:50.800 --> 0:04:54.159 is you're photographing. Remember when we see things, we're seeing 0:04:54.240 --> 0:04:57.599 light bouncing off of that and the color of the 0:04:57.600 --> 0:05:01.599 stuff we see is dependent upon and which frequencies of 0:05:01.800 --> 0:05:06.360 light bounce off of that thing. So then the shutter 0:05:06.440 --> 0:05:09.320 closes on your camera and you've got your chemical record. 0:05:09.560 --> 0:05:12.440 And the shutter is necessary because, as I said, these 0:05:12.520 --> 0:05:15.560 chemicals react to light. If you just had this stuff 0:05:15.600 --> 0:05:19.120 exposed to light all the time, it would have already reacted. 0:05:19.120 --> 0:05:20.640 You would not be able to use it to take 0:05:20.680 --> 0:05:23.360 a photograph of anything if you want to learn more 0:05:23.400 --> 0:05:27.760 about this process, which is fascinating, but really the process 0:05:27.800 --> 0:05:30.039 of photography is far enough out of the scope of 0:05:30.040 --> 0:05:32.280 this episode that I don't want to go into it 0:05:32.480 --> 0:05:37.279 much further. I do recommend you go to HowStuffWorks dot com. 0:05:37.320 --> 0:05:40.760 That's my old employer. I don't technically work for How 0:05:40.760 --> 0:05:44.080 Stuff Works anymore, but you can go to that website 0:05:44.240 --> 0:05:47.679 and you look up the article how Photographic Film Works. 0:05:47.920 --> 0:05:50.640 It was written by Chuck Woodworth and it's a great 0:05:50.800 --> 0:05:53.920 example of the how Stuffworks style, and it goes into 0:05:53.960 --> 0:05:58.120 the chemistry and physics of the photographic process, but we'll 0:05:58.160 --> 0:06:00.240 skim over the rest of that for the purpose of 0:06:00.279 --> 0:06:04.000 this episode. So now the film on the camera has 0:06:04.080 --> 0:06:07.480 a latent image on it, and it represents the moment 0:06:07.640 --> 0:06:10.880 in time the shutter allowed light to pass from the 0:06:10.960 --> 0:06:14.440 lens to hit the film. But in a film camera, 0:06:14.600 --> 0:06:18.919 a cinema camera, you're talking about a series of latent images. 0:06:19.560 --> 0:06:23.919 Motors pull this strip of film at a steady speed 0:06:24.520 --> 0:06:27.760 through the frame of the camera, where the shutter opens 0:06:27.760 --> 0:06:33.200 and closes at a regular frequency, and the standard speed 0:06:33.640 --> 0:06:38.039 of capturing images is twenty four frames per second. So 0:06:38.120 --> 0:06:43.040 a film camera is capturing twenty four photographs every second. 0:06:43.160 --> 0:06:46.000 The latent images need some processing in order to create 0:06:46.040 --> 0:06:48.800 something that can be fed through a film projector. The 0:06:48.839 --> 0:06:52.040 development process creates a negative image of the chemical record, 0:06:52.600 --> 0:06:55.720 and that means that the darkest areas of the image 0:06:55.760 --> 0:06:58.840 represent the spots where the film received the most light. 0:06:59.240 --> 0:07:02.480 It's the opposite of what you would expect, right. Anything 0:07:02.520 --> 0:07:05.440 that would be dark in a photograph will be light 0:07:05.520 --> 0:07:08.479 on a negative and vice versa. This negative has to 0:07:08.520 --> 0:07:10.800 be transferred onto another role of film to create a 0:07:10.840 --> 0:07:13.200 positive image in a process that I'm also not going 0:07:13.240 --> 0:07:15.560 to cover because we need some time for actual topic. Right. 0:07:16.160 --> 0:07:18.920 So when we watch a film, we have the perception 0:07:19.040 --> 0:07:22.840 that what we're viewing are moving objects up on a screen, 0:07:23.320 --> 0:07:26.680 but that is an illusion. What we're really seeing with 0:07:26.800 --> 0:07:30.600 true film is that it's a series of photographs. The 0:07:30.640 --> 0:07:33.480 projector is playing those photographs at the same speed that 0:07:33.560 --> 0:07:36.240 the film camera used to make them twenty four frames 0:07:36.280 --> 0:07:40.240 per second usually. I mean, if you want to play 0:07:40.240 --> 0:07:42.600 stuff in slow motion, then you would shoot a film 0:07:42.640 --> 0:07:45.480 at a much higher frame rate, like forty eight frames 0:07:45.520 --> 0:07:48.240 per second, but you would play it back at the 0:07:48.280 --> 0:07:51.440 standard twenty four frames per second, and that would give 0:07:51.480 --> 0:07:55.760 you the slow motion effect. And back in the old days, 0:07:56.160 --> 0:08:00.240 cameras were hand cranked, so you would get kind end 0:08:00.240 --> 0:08:03.680 of twenty four frames per second, but this would result 0:08:03.760 --> 0:08:06.520 in sort of that hurky jerky movement we associate with 0:08:06.640 --> 0:08:12.200 old movies that was hand cranked cinematography, and sometimes people 0:08:12.280 --> 0:08:15.400 would turn the crank a little faster or a little 0:08:15.440 --> 0:08:18.440 slower than others, so you don't really have a consistent 0:08:19.080 --> 0:08:22.160 experience there, because the playback speed, especially if you're playing 0:08:22.160 --> 0:08:25.320 it in a modern projector, is going to be standard, 0:08:25.360 --> 0:08:29.280 even if the recording speed wasn't. But never mind all that. 0:08:29.360 --> 0:08:32.760 If you were to stop the projector's reels at any 0:08:32.800 --> 0:08:35.480 given moment in the playback of a film, you would 0:08:35.520 --> 0:08:38.920 see a still image. You would advance the reel by 0:08:38.920 --> 0:08:41.520 one frame, and you would see the next image, the 0:08:41.559 --> 0:08:44.880 next photograph in that series, and you would likely be 0:08:44.920 --> 0:08:47.959 able to pick out how things are slightly different from 0:08:48.080 --> 0:08:50.760 the first frame you looked at and the next frame. 0:08:51.240 --> 0:08:53.920 And this is the same principle that's behind animation. If 0:08:53.960 --> 0:08:56.200 you've ever taken a pad of sticky notes and you 0:08:56.320 --> 0:08:59.679 drawn little figures on page after page after page that 0:08:59.720 --> 0:09:02.560 when you flip the pages, you get a simple little cartoon, 0:09:02.880 --> 0:09:06.360 then you've engaged in the same art form as great cinematographers. 0:09:06.559 --> 0:09:08.640 Then maybe your work was even better than theirs. I'm 0:09:08.640 --> 0:09:10.960 not one to judge. Now, why would I go to 0:09:11.000 --> 0:09:13.439 the trouble to cover the basics of film? Well, it's 0:09:13.480 --> 0:09:16.120 because the very nature of film inspired certain people to 0:09:16.400 --> 0:09:19.800 experiment with it, to try stuff that would be impossible 0:09:19.840 --> 0:09:22.600 to replicate in a real world setting, or at least 0:09:22.840 --> 0:09:27.360 it would be really difficult. Film wasn't a substitution for 0:09:27.400 --> 0:09:30.800 a theater. In theater, you can create a few interesting effects. 0:09:31.080 --> 0:09:35.040 Generally your options are limited to things like lighting tricks, 0:09:35.240 --> 0:09:39.080 maybe some creative sets or costumes, maybe an even a 0:09:39.120 --> 0:09:42.400 stage illusion or two, and perhaps some sound design. But 0:09:42.480 --> 0:09:46.200 with film there were other possibilities, and one fellow who 0:09:46.240 --> 0:09:52.400 recognized those possibilities was the French filmmaker and illusionist George Mellier. 0:09:53.000 --> 0:09:55.960 He was born in Paris, You know Paris in eighteen 0:09:56.040 --> 0:09:59.319 sixty one. Let that sink in for a moment. This 0:09:59.400 --> 0:10:03.000 man was born while the Civil War was going on 0:10:03.120 --> 0:10:07.640 in the United States. He became interested in stagecraft and magic, 0:10:07.720 --> 0:10:11.320 and by the eighteen nineties he was a successful stage magician. 0:10:11.840 --> 0:10:14.880 In eighteen ninety five, he saw an early film exhibition 0:10:14.960 --> 0:10:18.520 made by the Lumier Brothers and he became entranced by 0:10:18.520 --> 0:10:22.160 this new medium. His experience and illusions encouraged him to 0:10:22.160 --> 0:10:25.559 find ways to experiment with film to achieve new effects, 0:10:25.800 --> 0:10:28.960 stuff that wouldn't be possible to do in the real world. 0:10:29.559 --> 0:10:32.760 He was a special effects and film pioneer. He established 0:10:32.800 --> 0:10:37.839 methods to shoot slow motion, stop motion animation, to do dissolves, 0:10:37.880 --> 0:10:42.920 and tricks like superimposition and double exposure. Around eighteen ninety eight, 0:10:43.200 --> 0:10:46.040 Melier had a really cool idea. He wanted to create 0:10:46.080 --> 0:10:49.200 a truly bizarre special effect in which an actor would 0:10:49.200 --> 0:10:53.520 appear to remove his own head on screen. But how 0:10:53.520 --> 0:10:57.520 would he accomplish this? While the secret was in shooting 0:10:57.600 --> 0:11:01.679 multiple exposures of the same real film. Typically, after you 0:11:01.720 --> 0:11:04.400 expose film to light, you want to avoid doing that 0:11:04.480 --> 0:11:07.920 again because you will interfere with that chemical record. You know, 0:11:07.960 --> 0:11:10.680 if you were to ever take photographs with a film 0:11:10.760 --> 0:11:13.960 camera and then someone were to open up the back 0:11:14.000 --> 0:11:18.120 of the camera and expose the film to regular light, 0:11:18.800 --> 0:11:21.880 you could potentially ruin shots that were already made, plus 0:11:21.960 --> 0:11:24.840 ruin the film for the next couple of shots. It's 0:11:24.920 --> 0:11:28.080 not something that you typically want to do. More light 0:11:28.160 --> 0:11:32.640 will cause further reactions, chemical reactions on the actual plastic film, 0:11:32.679 --> 0:11:35.800 and your shot gets ruined. If you've ever used the 0:11:35.920 --> 0:11:39.040 cameras that don't quite line up the film properly at 0:11:39.080 --> 0:11:41.160 the very beginning or the very end, you might even 0:11:41.200 --> 0:11:44.800 notice that a couple of photos on those sections of 0:11:44.880 --> 0:11:49.079 the film role have two sets of images super imposed 0:11:49.120 --> 0:11:52.720 on top of one another, and that's because that little 0:11:52.760 --> 0:11:56.440 section of film was exposed more than once. Melia did 0:11:56.440 --> 0:12:00.120 this on purpose. He would set up a shot and 0:12:00.160 --> 0:12:02.240 he would use a lens that had some of the 0:12:02.360 --> 0:12:06.000 lens blacked out so that light could not pass through 0:12:06.120 --> 0:12:08.720 that part of the lens. And we refer to this 0:12:08.960 --> 0:12:12.960 as a mat matte, and you can think of it 0:12:13.040 --> 0:12:15.960 like a mask for the lens, and that would mean 0:12:16.000 --> 0:12:18.640 a section of each frame corresponding to that part of 0:12:18.640 --> 0:12:21.480 the mat would remain unexposed to light. He would shoot 0:12:21.520 --> 0:12:25.720 the scene as rehearsed. Afterward, he would rewind the exposed 0:12:25.760 --> 0:12:27.880 film in the camera, beat it right back in as 0:12:27.920 --> 0:12:29.880 if he was going to shoot something all for the 0:12:29.920 --> 0:12:34.560 first time, and he would then replace this mat with 0:12:34.640 --> 0:12:37.680 a new one and the new mat would block out 0:12:37.920 --> 0:12:43.600 everything except the section that previously was unexposed. So in 0:12:43.600 --> 0:12:46.559 other words, the part that was black would now be clear, 0:12:46.920 --> 0:12:50.400 and the rest of the lens that was previously unblacked 0:12:50.600 --> 0:12:53.200 would be blacked. So you replace one mat with a 0:12:53.240 --> 0:12:56.520 different one. So he would then be able to film 0:12:56.559 --> 0:12:58.960 something totally new into this same role of film, and 0:12:59.000 --> 0:13:02.120 this time the would pick up a new scene and 0:13:02.160 --> 0:13:04.440 by changing things between one section and the other, he 0:13:04.440 --> 0:13:07.760 could create weird effects like the head removal trick. It 0:13:07.760 --> 0:13:10.440 would appear as though all of this was shot at 0:13:10.480 --> 0:13:12.880 the same time on the same role of film, but 0:13:13.000 --> 0:13:15.960 in fact, through careful control of where the light would go, 0:13:16.280 --> 0:13:20.880 Melia would use the same film twice or more to 0:13:20.960 --> 0:13:23.360 produce cool results. And if you want to see an 0:13:23.360 --> 0:13:26.840 example of what I'm talking about, and I highly recommend 0:13:26.840 --> 0:13:29.320 you check this out because it is amazing even today, 0:13:30.120 --> 0:13:32.960 go to YouTube and do a search for the short 0:13:32.960 --> 0:13:37.480 film four Heads Are Better than One. The creativity of 0:13:37.480 --> 0:13:40.800 this film, which by the way, lasts less than a minute, 0:13:41.320 --> 0:13:45.800 is still astonishing. To say his experimental work was influential 0:13:46.559 --> 0:13:50.200 would be a gross understatement. Other filmmakers, inspired by the 0:13:50.200 --> 0:13:53.880 work of Melia tried new techniques that built upon the 0:13:53.920 --> 0:13:59.280 foundation he established. For example, filmmaker and documentarian Norman Dawn 0:13:59.440 --> 0:14:03.520 wanted to show films at historic buildings around California, but 0:14:04.080 --> 0:14:08.120 several of those buildings had been damaged or even partly destroyed. 0:14:08.720 --> 0:14:12.800 Other historic buildings had modern stuff like light poles in 0:14:12.800 --> 0:14:14.760 front of them. He didn't want that to be in 0:14:14.800 --> 0:14:17.480 the shot, so he wanted to show the buildings as 0:14:17.520 --> 0:14:21.400 they had appeared in their original form before the decay, 0:14:21.560 --> 0:14:26.400 before modern technology had advanced into the area. So he 0:14:26.520 --> 0:14:30.600 came up with a really clever idea. Dawn placed a 0:14:30.640 --> 0:14:34.040 pane of glass between the camera and the scene he 0:14:34.160 --> 0:14:37.520 wanted to shoot, and on that pane of glass he 0:14:37.600 --> 0:14:41.480 had paintings to enhance the scene. If a building's roof 0:14:41.480 --> 0:14:43.760 had caved in, he would frame up the shot and 0:14:43.760 --> 0:14:46.320 then have an artist paint a roof on the glass 0:14:46.480 --> 0:14:49.480 so that when viewed through the camera, the painting and 0:14:49.520 --> 0:14:52.440 the building behind it would line up and the building 0:14:52.480 --> 0:14:55.040 would appear to be whole again. Or he might want 0:14:55.080 --> 0:14:57.720 to cover up stuff like those telephone poles. He would 0:14:57.760 --> 0:15:01.000 have an artist paint trees on the so from the 0:15:01.000 --> 0:15:05.240 camera's perspective the polls were hidden. His process also involved 0:15:05.360 --> 0:15:09.320 double exposures. This was an example of a Matt painting, 0:15:09.760 --> 0:15:12.680 and he would claim credit for inventing this, and he 0:15:12.760 --> 0:15:15.920 even applied for a patent on it. But subsequent lawsuits 0:15:16.000 --> 0:15:19.160 established that other filmmakers were using similar approaches, and the 0:15:19.200 --> 0:15:23.240 patent office ultimately denied the claim, but Matt paintings would 0:15:23.240 --> 0:15:26.200 become an important part of filmmaking from that point forward. 0:15:26.840 --> 0:15:30.960 One disadvantage to these early film effects was they required 0:15:30.960 --> 0:15:34.040 the camera to remain stationary through the whole process. You 0:15:34.080 --> 0:15:37.440 couldn't move the camera at all, or else your shots 0:15:37.440 --> 0:15:40.320 wouldn't line up, so you wanted the camera to remain 0:15:40.360 --> 0:15:43.760 in one place through all of these different exposures. Another 0:15:43.800 --> 0:15:46.960 problem was that no action could cross the Matt line 0:15:47.040 --> 0:15:49.720 because it would get cut off as it moved beyond 0:15:50.200 --> 0:15:54.720 that invisible at least from the audience's perspective line. Now, 0:15:54.800 --> 0:15:57.440 let's move on up to nineteen eighteen, when a guy 0:15:57.520 --> 0:16:03.360 named Frank Williams created the Williams process, which honestly seems 0:16:03.400 --> 0:16:07.520 pretty convenient to me. The Williams process allowed for more 0:16:07.600 --> 0:16:11.440 movement and involved shooting actors against a solid background such 0:16:11.480 --> 0:16:16.320 as a black or blue curtain on very high contrast film. 0:16:16.720 --> 0:16:21.400 The process sometimes required multiple transfers onto new film until 0:16:21.440 --> 0:16:25.800 you arrived at a black silhouette against a pure white background, 0:16:25.880 --> 0:16:28.400 the negative image of what you were shooting before, and 0:16:28.440 --> 0:16:31.120 this was called a holdout matt. The way these transfers 0:16:31.160 --> 0:16:33.560 typically would work is that you would put one strip 0:16:33.680 --> 0:16:37.600 of shot developed film into a camera, so you've already 0:16:37.600 --> 0:16:39.520 shot on it, but you're putting it through the camera again. 0:16:40.360 --> 0:16:44.800 And you would put a second strip of film that 0:16:45.040 --> 0:16:49.480 is unshot, it's unprocessed, no lights hit it, and put 0:16:49.520 --> 0:16:53.360 it right up against the first developed piece of film. 0:16:53.600 --> 0:16:56.600 You would shine light through the camera and you would 0:16:56.680 --> 0:17:00.000 let it just run. And this way you would transfer 0:17:00.080 --> 0:17:04.000 for the images from one strip to the other. And 0:17:04.480 --> 0:17:07.800 this was called bypacking because you were putting two different 0:17:07.880 --> 0:17:11.960 pieces of film through the camera to achieve this process. 0:17:12.400 --> 0:17:15.240 And you could also do this not just with developed 0:17:15.240 --> 0:17:17.760 film where you're making copies. You could do it with negatives. 0:17:17.760 --> 0:17:21.240 You could do it in a way to increase contrast 0:17:21.359 --> 0:17:24.120 from copy to copy until you were able to create 0:17:24.480 --> 0:17:28.680 a holdout mat reverse printing. The holdout matt creates a 0:17:28.720 --> 0:17:32.920 white silhouette on a black background or a cover mat. 0:17:33.000 --> 0:17:35.960 So now you've got a holdout matt and a cover mat. 0:17:36.240 --> 0:17:39.040 You would take the footage of a previously shot background. 0:17:39.119 --> 0:17:41.760 Let's say it's a foreboding forest, so you've shot your 0:17:41.800 --> 0:17:44.640 actors in a sound stage, but you want the background 0:17:44.640 --> 0:17:47.600 to be this really scary looking forest, and you would 0:17:47.600 --> 0:17:51.000 bypack a film camera with the background footage that you 0:17:51.040 --> 0:17:55.920 had shot and the black silhouette holdout matt of the 0:17:56.200 --> 0:17:59.840 actor's footage that you shot. Then you would transfer this 0:18:00.080 --> 0:18:04.440 combination to a third piece of unexposed film by again 0:18:04.520 --> 0:18:07.360 shining a light through those other two pieces. And because 0:18:07.400 --> 0:18:11.760 the background on the holdout mat is white, the light 0:18:11.880 --> 0:18:14.560 passes through it easily and it hits the previously shot 0:18:14.600 --> 0:18:17.720 background image that comes through and gets copied onto the 0:18:17.720 --> 0:18:22.360 blank film. The silhouette of your actors is black that 0:18:22.400 --> 0:18:26.760 prevents light from passing through. So the previously blank third 0:18:26.800 --> 0:18:29.720 piece of film now has a background image and this 0:18:29.880 --> 0:18:33.840 dark silhouette of actors moving through the frame. Then you 0:18:33.840 --> 0:18:36.840 would have to take that piece of film that has 0:18:36.880 --> 0:18:39.399 this black silhouette and you have to bypack it with 0:18:39.440 --> 0:18:42.119 the original footage of the actor, not the silhouette, but 0:18:42.160 --> 0:18:45.919 the actual actor footage. And now the real actor is 0:18:46.000 --> 0:18:48.600 on top of the silhouette and appears to actually be 0:18:48.840 --> 0:18:51.200 in front of whatever the background image is, in our case, 0:18:51.240 --> 0:18:55.280 the foreboding forest. Because this type of matt moves from 0:18:55.320 --> 0:18:59.000 frame to frame, it's called a traveling mat. And if 0:18:59.040 --> 0:19:02.720 you remember Fraggle Rock you might remember Traveling Matt is 0:19:02.760 --> 0:19:06.560 the name of Gobo's uncle. Gobo, by the way, is 0:19:06.600 --> 0:19:09.600 another stage and lighting term. It stands for a template 0:19:09.760 --> 0:19:12.960 or stencil that controls the shape of a lamps emitted light. 0:19:13.800 --> 0:19:19.199 So some of the Fraggles had fun industry names, Gobo 0:19:19.280 --> 0:19:22.600 and traveling Matt. When we come back, we will continue 0:19:22.680 --> 0:19:26.320 down the history of how chroma key came about. But 0:19:26.359 --> 0:19:37.600 first let's take a quick break. Before the break, I 0:19:37.680 --> 0:19:41.479 was talking about the Williams process, but C. Dodge Dunning 0:19:41.520 --> 0:19:45.280 would improve upon the Williams process by using yellow light 0:19:45.359 --> 0:19:47.439 to shoot the actor in front of a blue screen, 0:19:48.040 --> 0:19:52.000 creating the Dunning process, and this was used extensively in 0:19:52.040 --> 0:19:55.560 the classic nineteen thirty three film King Kong, and they 0:19:55.640 --> 0:19:57.879 weren't great for black and white film. Remember this is 0:19:57.920 --> 0:20:01.840 before anyone was shooting on color. So although I mean 0:20:01.880 --> 0:20:04.840 there were ways of treating film to create color, but 0:20:04.920 --> 0:20:07.640 this was standard black and white film, so you didn't 0:20:07.680 --> 0:20:10.800 have to worry about the weird lighting. But if you 0:20:10.840 --> 0:20:12.920 wanted to shoot in color, that was going to cause 0:20:13.359 --> 0:20:18.440 or require other considerations. Around the same time, engineers were 0:20:18.480 --> 0:20:22.600 developing the optical printer, which really simplified the process of 0:20:22.600 --> 0:20:25.719 transferring images from one strip of film to another. Now 0:20:25.760 --> 0:20:30.879 I talked about bypacking, but the optical process could be 0:20:31.240 --> 0:20:34.639 an alternative to that. It didn't eliminate it, but it 0:20:34.720 --> 0:20:37.480 was a different way to achieve the same thing. Essentially, 0:20:38.119 --> 0:20:42.000 an optical printer has a projector on one side and 0:20:42.040 --> 0:20:45.119 a camera on the other. The projector shoots out a 0:20:45.119 --> 0:20:48.400 projected image that then gets copied onto a new, unexposed 0:20:48.480 --> 0:20:50.879 role of film inside the camera. And it also allowed 0:20:50.880 --> 0:20:53.919 filmmakers to create new effects by changing the focal point 0:20:54.160 --> 0:20:56.879 of the camera or the distance between the projector and 0:20:56.920 --> 0:20:59.959 the camera. And rather than bypacking camera, you just use 0:21:00.160 --> 0:21:03.720 this process you could get better results. The first mass 0:21:03.720 --> 0:21:06.960 produced optical printer hit the market in the mid nineteen forties. 0:21:07.200 --> 0:21:10.440 It came from a company called Acme Donne. In addition, 0:21:10.600 --> 0:21:15.440 filmmakers created rear projection backgrounds, so in these actors would 0:21:15.480 --> 0:21:19.320 perform in front of a screen like a projection screen, 0:21:19.520 --> 0:21:23.119 not a green screen or a blue screen, and behind 0:21:23.400 --> 0:21:26.640 that screen would be a film projector and it would 0:21:26.640 --> 0:21:31.200 provide a projected background image. You could do this in 0:21:31.240 --> 0:21:34.600 place of the processes have already described, putting your actors 0:21:34.640 --> 0:21:37.320 in front of a screen that shows whatever background you wanted. 0:21:37.680 --> 0:21:40.359 The background could be fairly static, but didn't have to be. 0:21:40.800 --> 0:21:45.199 You could include a background that was actually dynamic, showing movement. 0:21:45.359 --> 0:21:47.919 It could be a film in of itself. This was 0:21:48.000 --> 0:21:50.919 used a lot in shots where people were in vehicles 0:21:51.119 --> 0:21:54.040 and talking with one another. So rather than setting up 0:21:54.119 --> 0:21:56.720 a car on a trailer and shooting it in the 0:21:56.760 --> 0:21:59.400 real world with the camera on the trailer, or worse yet, 0:21:59.400 --> 0:22:01.480 trying to figure out how to fit a camera onto 0:22:01.520 --> 0:22:05.080 a real moving car that's operated by an actor, you 0:22:05.080 --> 0:22:08.679 would typically have performers sitting in a stationary vehicle and 0:22:08.760 --> 0:22:12.120 the screen behind and sometimes to either side of them 0:22:12.480 --> 0:22:16.160 would display previously shot footage of scenery going by from 0:22:16.200 --> 0:22:19.680 the correct perspective, as if the car were driving down 0:22:19.720 --> 0:22:23.080 the road. This wasn't necessarily convincing, mind you, but it 0:22:23.240 --> 0:22:27.399 was an interesting technique. In nineteen thirty two, engineers created 0:22:27.440 --> 0:22:32.880 a process to produce films in color called appropriately Technicolor. Interestingly, 0:22:33.200 --> 0:22:37.080 in this process, images would be captured to three strips 0:22:37.200 --> 0:22:40.199 of black and white film at this stage as the 0:22:40.440 --> 0:22:44.760 tri strip approach. This was not the original version of Technicolor. 0:22:44.800 --> 0:22:49.119 It was technically the fourth incarnation of the Technicolor technology, 0:22:49.119 --> 0:22:52.560 but it's the important one for our discussion. So how 0:22:52.600 --> 0:22:56.159 do you produce a color image if you're using black 0:22:56.200 --> 0:22:59.600 and white film as your medium? Well, first you have 0:22:59.640 --> 0:23:03.840 to shoot your footage. And inside an early Technicolor tri 0:23:04.040 --> 0:23:09.199 strip camera behind the lens was an optical cube and 0:23:09.240 --> 0:23:12.920 it acted as a prism. Prisms break up incoming light 0:23:13.040 --> 0:23:17.919 into bands of frequencies, and you've likely had one, or 0:23:17.960 --> 0:23:20.440 played with one, or at least seen one. That's the 0:23:20.520 --> 0:23:21.879 kind of stuff, you know. A light goes through it 0:23:21.920 --> 0:23:24.000 and then it makes rainbows. You see a little rainbow 0:23:24.040 --> 0:23:28.520 pattern projected somewhere. This prism would break up the incoming 0:23:28.600 --> 0:23:32.199 light into three general bands that corresponded with red, green, 0:23:32.320 --> 0:23:35.920 and blue. Each of those bands of light would hit 0:23:36.040 --> 0:23:39.000 one of three strips of black and white film inside 0:23:39.000 --> 0:23:42.080 the camera, so one strip of film would be exposed 0:23:42.119 --> 0:23:44.880 to all the red light coming from a scene, one 0:23:44.920 --> 0:23:47.080 from all the green light coming from a scene and 0:23:47.160 --> 0:23:49.840 one from the blue. The concentration of each color in 0:23:49.880 --> 0:23:52.680 the scene would affect how much light was hitting each 0:23:52.800 --> 0:23:55.920 strip of film, So you'd end up with three negatives 0:23:56.000 --> 0:24:00.439 of your scene that were all perfectly synchronized, all of 0:24:00.480 --> 0:24:04.040