WEBVTT
Kind: captions
Language: en-GB

1
00:00:00.099 --> 00:00:04.350
These days, green screen is easy. You get
your lighting right, you point a camera at

2
00:00:04.350 --> 00:00:07.129
someone, and then you click a few buttons
and tweak a few settings in your graphics

3
00:00:07.129 --> 00:00:09.210
software, and there you go. Perfect.

4
00:00:09.210 --> 00:00:13.510
But how did they do this sort of compositing
before computers?

5
00:00:13.510 --> 00:00:18.000
Well, there are two answers to that. One for
film, and one for video. And before anyone

6
00:00:18.000 --> 00:00:22.680
gets pedantic: I'm summarising here, and skipping
over some early efforts and dead ends, but

7
00:00:22.680 --> 00:00:28.220
first, let's talk about film. Actual, bulky
reels of film. You've got no pixels to deal

8
00:00:28.220 --> 00:00:32.809
with there: it's all chemical processes, all
light hitting bits of photosensitive real

9
00:00:32.809 --> 00:00:39.039
stuff twenty-four times a second. If you go
wrong, you can't erase and restart, that film's

10
00:00:39.039 --> 00:00:41.260
used up. Gone. Go buy some more.

11
00:00:41.260 --> 00:00:45.629
Anyway, the earliest method for this sort
of effect involved filming an actor against

12
00:00:45.629 --> 00:00:50.289
black, and then making copies of that film with
higher and higher and higher contrast, until you had

13
00:00:50.289 --> 00:00:55.809
a simple matte. With that, you could pull
off a double exposure, using chemical trickery

14
00:00:55.809 --> 00:01:00.039
and something called an optical printer to
leave a hole in the background picture where

15
00:01:00.039 --> 00:01:03.649
the actor would then be slotted in. Or part
of the actor, if we're talking about Claude

16
00:01:03.649 --> 00:01:05.280
Rains as the Invisible Man.

17
00:01:05.280 --> 00:01:10.979
Right. Variations on that high-contrast technique
were used for decades. The next major breakthrough

18
00:01:10.979 --> 00:01:15.299
was the travelling matte. The cleverest version
of this was bought up by Disney, who owned

19
00:01:15.299 --> 00:01:20.240
the only camera in the world that could pull
it off. They lit the actors normally, but

20
00:01:20.240 --> 00:01:25.479
put them in front of a white background lit
with sodium vapor lights -- orange streetlights.

21
00:01:25.479 --> 00:01:29.820
Sodium light is monochromatic at one very
specific wavelength -- so with some fancy

22
00:01:29.820 --> 00:01:33.609
optics, you could simultaneously record onto
one piece of film that would mostly ignore

23
00:01:33.609 --> 00:01:38.929
that light and another bit of film that only
reacted to that light. Presto: a near-perfect

24
00:01:38.929 --> 00:01:44.310
travelling matte, even for semi-transparent
objects like Mary Poppins' hat.

25
00:01:44.310 --> 00:01:49.219
Bluescreen and greenscreen on analogue film
work much the same way. They use filters to

26
00:01:49.219 --> 00:01:52.820
block out particular colours and matte them,
and then they're carefully combined with an

27
00:01:52.820 --> 00:01:57.479
optical printer. Then, of course, computers
came along and made the whole thing easier.

28
00:01:57.479 --> 00:02:02.249
How about television? Computers arrived earlier
than you might think here; the BBC used a

29
00:02:02.249 --> 00:02:07.229
bit of kit called the Quantel Paintbox for
Doctor Who as early as 1980. But before that,

30
00:02:07.229 --> 00:02:11.660
video was entirely about electrical signals
from a scanning camera sensor -- if it was

31
00:02:11.660 --> 00:02:15.380
recorded, those signals would just be put
straight on magnetic tape. There's no film

32
00:02:15.380 --> 00:02:16.650
to play about with there.

33
00:02:16.650 --> 00:02:21.060
But what you could do with electronic signals
is combine them and build circuits that basically

34
00:02:21.060 --> 00:02:25.270
do analogue maths on them. Adding two signals
together, or just fading between them, was

35
00:02:25.270 --> 00:02:30.340
mastered early in the days of black and white
TV. Now, when colour came along, you had red,

36
00:02:30.340 --> 00:02:33.760
green, and blue signals -- although they weren't
transmitted over the air like that, for backwards

37
00:02:33.760 --> 00:02:37.740
compatibility, it's a long and overly-complicated
story -- but you could make a system that

38
00:02:37.740 --> 00:02:41.920
would watch the signal, and when it hit a
particular colour -- the colour you wanted -- it'd

39
00:02:41.920 --> 00:02:47.060
switch out that signal with your background
one. And generally, this was done live on

40
00:02:47.060 --> 00:02:52.410
set. There were even attempts to do moving
shots by rigging up really complicated gearing arrangements

41
00:02:52.410 --> 00:02:57.980
to sync the movements of two cameras -- one
pointing at actors on a bluescreen, one pointing

42
00:02:57.980 --> 00:03:00.800
at a model. It even worked sometimes.

43
00:03:00.800 --> 00:03:05.700
No pixels. No memory or hard drives, no ability
to just tweak your settings and try something

44
00:03:05.700 --> 00:03:09.990
else: if it didn't work, well you did the best
you could, because every day in the studio

45
00:03:09.990 --> 00:03:13.700
cost an incredible amount of money and the
time of at least half a dozen technicians.

46
00:03:13.700 --> 00:03:18.300
And then, of course, computers came along
and made all of that obsolete, to the point

47
00:03:18.300 --> 00:03:22.870
where some jerk with a laptop and a copy of
After Effects can make this video in an afternoon.

48
00:03:23.800 --> 00:03:25.800
[Translating this video? Add your name here if you'd like credit!]