310 Moving Images: Making Movies, Understanding Mediaillusions, from a wide variety of matte shots, front and rear projection, and
chroma key (bluescreen and greenscreen) technology. A common technique
that has been augmented by digital technology is the use of color screens—
particularly green or blue (used mainly because of their absence in skin
tones)—to combine two images seamlessly. With this method, actors stand
in front of the screen of green or blue, which is the color, or “chroma key,”
that will be removed. Th e green or blue in the image is made transparent
so the actors appear to be standing in front of whatever image is inserted as
background.
Amazingly, this technique was developed for Th e Th ief of Baghdad, which
was in production in London at the beginning of World War II! Producer
Alexander Korda staked a substantial investment on his trust in American visual
eff ects director Larry Butler, who boldly believed his new technique would
work, despite absolute rejection by offi cials from the Technicolor Company.
Th eir daring gamble paid off , and it serves as one of the fi nest examples of
the mix of entrepreneurship, artistry, technical innovation, and collaboration
that embodies the story of fi lmmaking. Chroma key techniques are used in
many types of motion pictures, from complex feature fi lm productions to
television weather reports. Use of such technology can involve many aspects
of the production process, and the collaborative nature of fi lmmaking is
vividly seen in such aspects of production.
More recently, the use of greenscreens has become standard because
digital image sensors have a higher sensitivity to green. Interestingly, for the
2002 fi lm Spider-Man, visual eff ects supervisor John Dykstra had to oversee
the use of both bluescreen and greenscreen. Th is was because Spiderman,
whose costume has lots of blue, needed a greenscreen, while the Green Goblin
had to be photographed in front of a bluescreen or the process would not
have worked eff ectively.Figure 8-28 Chroma key
work in the studio on Spider-
Man 2, with director Sam
Raimi instructing James
Franco (on ground) and
Alfred Molina perched for
action. (Courtesy Columbia
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