Movie Making History of Blue and Green Screen Effects


Uploaded by videomaker on 12.12.2008

Transcript:
bjbj This time on tips and tricks we re gonna take a look at the history of Chroma Key,
how the process began, and how film producers used this process over the years to help them
cinematically. Everything from blue screen to green screen, this time on tips and tricks.
The history of Chroma Keying is based on the need to have the control and convenience of
shooting on a set married with the beauty of shooting on location. Location shooting,
ranging from the extremely difficult say the middle of the ocean to the impossible say
a battle scene in deep space are the prime instances where Chroma Keying comes into play.
The idea of being able to separate the foreground and seamlessly integrate another background
has driven some of the best minds in the film and TV business to come up with various solutions
over the years. Originally developed in the 1930s by RKO Radio Picture, producers used
a process that combines two or more images into one known as a traveling mat. This process
was pioneered by Linwood Dunn. He used traveling mat and double exposure to create transitions
in such films as the 1933 musical Flying Down to Rio. The effects of double exposure had
been known for some time, but Dunn s attempt at minimizing the background of the second
exposure by using a traveling mat took a big leap forward in believability. The process
involved projecting the background image onto a counter mat and then optically re-photographing
the result. While not perfect as you can see some bleed through in the airplane, it was
pretty impressive for 1933, and the audiences bought into the effect. Special effects mastermind
Larry Butler is largely credited with the creation of blue screen during a fantasy film,
The Thief of Baghdad. Released in 1940 by London Films, the film was the first of its
kind to feature dazzling special effects as well as Technicolor. When color film became
available it opened the door to new advances in Keying, and The Thief of Baghdad was the
first film to use the Chroma Key process. By using three strips of film, one for red,
one for green, and one for blue, Butler was able to arrange the original negative and
newly printed positive strips in such a way that the blue negative and green positive
film strips created a pretty solid mat that could be composited with new footage shot
against a blue screen. These were all run through an optical printer so that the final
film print would show the finished composite. While not yet a perfect Key due to the limitations
of the equipment at the time, the basic concept was used in color film compositing until the
advent of digital technology. Arthur Windermere began to develop even more blue screen techniques
by creating the ultraviolet traveling mat process in the 1958 adaptation of the Ernest
Hemingway novel, The Old Man and the Sea. Unfortunately the process was extremely time-consuming,
as the film had to be combined one frame at a time. The Chroma Key process was finally
perfected by Richard Edlund after he created a quad-optical printer for The Empire Strikes
Back in 1980. The quad-optical printer was the key to taking a rough analog process,
making it easier and much more accurate with better results for the final shot. Two projectors,
a film camera, and a beam splitter combined the images together one frame at a time. This
part of the process had to be very carefully controlled to ensure the absence of black
lines. During the 1980s many computers were used to control the optical printer to get
it just right. The switch from blue screen to green screen largely reflects the switch to video in the
late 70s. Although blue screen is very complementary to human skin tone and better with film due
to the blue emulsion layer film strips contain, green screen became the favorite in the video
world because digital cameras retain more detail in the green color channel. It also
requires less light and has a higher luminance value than blue. In the past decade the use
of green has become more dominant in video special effects. Also, the green background
is favored over blue for outdoor shooting, where the blue sky might appear in the frame
and could accidentally be replaced in the process. CGI, or computer generated imagery,
is now used for the majority of Hollywood releases. The principle is the same as working
with the green screen, the only difference being the backgrounds are constructed on a
computer instead of shooting an existing location. The effort that generations of filmmakers
put into special equipment and techniques in order to pull a good Key was intense and
difficult, requiring both artistic sense and a technical mastery of the media. So the next
time you shoot some green screen footage and simply click the Chroma Key effect with your
mouse, spare a thought for those uncelebrated men behind the scenes who made the whole process
possible. As you can see, green screen is still very popular and very useful in video
today. In our next segment we re gonna take a look at some simple tips and tricks on how
you can use this effect to make your videos. [End of Audio] History of Chroma Key Page
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