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Have you ever seen a movie and wondered, "How did they do that?" One reason why people go to movies is to be transported into a world where anything is possible. The art of special effects relies on how the human brain and eyes perceive the world. Like the magician who uses slight of hand, special effects use perspective and angles to trick the viewer into thinking that the scaled-down model—whether it's a gorilla, a spaceship, or the White House—is the real thing.
In the landmark 1933 monster movie King Kong, a 50-foot-tall
king of the jungle rampages through New York City. To make this
18-inch miniature look real, animator Willis O'Brien used stop-motion
animation. In this technique, the small-scale miniature Kong is
moved through a range of motions and photographed one frame at a
time with each movement. To create the illusion that the creature
is moving, the frames are simply projected at the regular film speed
of 24 frames per second.
When special effects designers re-created the Titanic ship
for the 1997 movie, they built one side of a ship, just 1/20 of
the scale of the big ship that went down in 1912. The real ship
was approximately 883 feet long. Actually, two 45-foot models were
created: one in perfect condition as it set sail, and one as it
looks today. Producers combined the small-scale model with footage
of white water and wakes and a matte painted sky background in a
computer, and voila, the Titanic appeared to be crossing
the Atlantic.
To make a scene like the White House explosion in the movie Independence
Day, cinematographers shot the film faster than the normal 24
frames per second. Ironically, to create slow motion, you shoot
the film faster. To judge how fast to shoot the film, directors
generally take the reciprocal of the square root of the scale. So
a model built at 1/16 scale would be shot 4 times as fast (the square
root of 16) as normal. When you see the shot in slow motion, it
looks as though it were a full-size explosion.
Like opening the curtain on the Wizard of Oz, uncovering the secrets
of special effects is sometimes disheartening. But have no fear,
the special effects "wizards of ahs" will no doubt continue to leave
you wondering, "How did they do that?"
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