Camcorders and movie cameras
Last updated: March 11, 2008.
Ordinary cameras
are brilliant for taking snapshots of the world. The only trouble is,
the world simply won't "sit still"—there's
always something moving around us, over our heads, or even under our
feet! Fortunately, movie cameras are able to capture moving images that
better reflect the changing nature of our world. Compact movie cameras
called camcorders are small and portable enough to take anywhere and,
because they use digital technology, you can easily edit the films they
take on your computer and even
upload them onto the Web.
Photo: A Canon XL1S digital video camcorder in
action. Note the boom microphone on top for recording high-quality
sound. You focus the image by turning the lenses at the front with your
fingers. Photo by John A. Lee, II by courtesy of Defense Visual
Information Center.
How the eye fools the brain
Open up a camcorder and you'll find all kinds of mechanical and
electrical parts packed inside. But the basic science behind making
movies has nothing to do with lenses, gears, electric motors, or
electronics—it's all about how our eyes and brains work.
You've probably done
that trick where you make a flip book by drawing little stick people on
the corner of a pad of paper and flicking them with your fingers so
fast that they hop, skip, and jump. When your eye sees a series of
still images (or "frames") in quick succession, it holds each image for
a little while after it disappears and even as the next one starts to
replace it. In other words, each picture leaks into the next one, so
they blur together to make a single moving image. This is known as the persistence of vision and it's the secret behind
every movie you've ever seen.
It's not just flick books that use persistence of vision. Before
movie cameras and projectors were invented, 19th-century toy makers
were using the same idea to make relatively crude animated films. A
typical toy from this era was called the zoetrope. It was a large
rotating drum with thin vertical slits cut into its outer edge. Inside,
you placed a long strip of paper with small colored pictures drawn on
to it. Then you rotated the drum to make the pictures blur together
(just like a flick book) and looked down through one of the slits to
watch them. Here's a great photo of a restored
zoetrope by Andrew Dunn.
From still photos to movies
It's a relatively small step from flip books and zoetropes to fully
fledged movies. The theory of making a movie is just as simple: you
take thousands and thousands of still photographs one after another.
When you play them back at high speed, they blur into a single moving
image—a movie.
A famous American photographer called Eadweard Muybridge (1830-1904)
was one of the first people
to show how one moving picture could be made from many still ones.
Using multiple cameras arranged in rows,
he took series of photographs of galloping horses and vaulting
gymnasts. Few things illustrate how movies work better than Muybridge's
amazing photos. Here's a sequence he made called horse in motion:
Photo courtesy of US Library
of Congress.
A movie camera or camcorder simply automates what Muybridge did by
hand. A basic movie camera is like a standard film camera that takes
a photograph on to plastic film every time the shutter opens and
closes. 
In a standard film camera, you have to wind the film on so it
advances to the next position to capture another photograph. But in a
movie camera, the film is constantly moving and the shutter is
constantly opening and closing to take a continuous series of
photographs—about 24 times each second. Before camcorders were
invented, people used mechanical home movie cameras, which were very
small versions of professional movie cameras with all the parts (and
the film itself) miniaturised. When video was invented, photographic
tape was replaced by magnetic videotape, which was simpler, cheaper,
and needed no photographic developing before you could view the films
you'd recorded. Mechanical movie cameras soon started to evolve into
convenient, modern, electronic video cameras.
Photo: At first glance, this old-style Arriflex
film camera looks quite like a
modern camcorder—but look closer. On top, you can see a big oval-shaped
case
where a huge reel of film is stored. If you were standing next to this
camera,
you would also be able to hear a motor inside whirring away as the film
rattled through the mechanism.
Photo by Dave Maclean, courtesy of Defense Visual
Information Center.
Modern camcorders use digital video. Instead of recording
photographic images, they use a light sensitive microchip called a charge-coupled device (CCD) to convert what the
lens sees into digital (numerical) format. In other words, each frame
is not stored as a photograph, but as a long string of numbers.
So a movie recorded with a digital camcorder is a series of frames,
each
stored in the form of numbers. In some camcorders, the digital
information is recorded onto videotape; in others, you record onto a
DVD; and in still others, you record
onto a
hard drive or
flash memory. The advantage of storing
movies in
digital format is that you can edit them on your computer, upload them
onto web sites, and view them on all kinds of different devices (from
cellphones and
MP3 players to
computers and
televisions). Try doing that with a silent
movie from the 1920s!
Photo: A professional Canon camcorder. Photo by
Kristi Mulder by courtesy of Defense Visual Information Center.
