18 PART 1 GETTING TO KNOW DIGITAL CAMERAS
How the Digital Camcorder
Captures Future Memories
The digital camcorder is not your father’s 8mm movie camera. Fifty years ago, family events
and vacations were recorded on narrow silent film that faded with the years and grew jerkier
each time it was fed through the home projector. Today, the family video camera comes within a
hairbreadth of producing movies—videos that are technically as good as you see in the theaters
or on a TV set. For all the similarities between digital video and still cameras, they are, for the
time being, different animals. Because the subjects in videos are constantly moving, the eye
doesn’t notice if the image is not as sharp as a good photo. But the two animals are evolving
into a new creature—one that builds in the different circuitry and mechanisms needed to shoot
both stills and motion.
The operator of a low- to mid-range digital camcorder has a
choice of equipment for framing a shot. A viewfinderwith
a magnifying glass in the end of it enlarges a small LCD
image that shows the lens’s vantage point, focus, and amount
of zoom, regardless of whether the camera is recording. The
method cuts out distraction and lets the photographer better
concentrate on the subject.The focused light from the lens falls on an image sensor, called a charge-coupled device (CCD),
orcomplementary metal-oxide semiconductor (CMOS)chip. Over the surface of the sensor lie
thousands of photodiodes, or pixels, each of which generates electrical current in proportion to the
brightness of the light that strikes it. Note that camcorders use fewer pixels than still cameras, which
count their pixels in the millions. Camcorders are more concerned with hustling images through the
system, at the rates of a dozen or two each second, than with image sharpness. In fact, the millions of
pixels in a camera would quickly be bottlenecked by the relative slowness with which camcorders can
store the visual information they gather.After an image processorin the camera massages the
visual data passed on by the sensor, the processor converts
the image to a system of numerical values that represent
different colors and hues. They are joined to similar digital
information coming from the camera’s microphone. The
combined signal is recorded, usually to magnetic tape.The second choice is a larger LCD
screen that can be twisted to any
position, even toward the front of
the camera so that the photogra-
pher can be in theframe, all the
while keeping an eye on what the
camera is seeing.The image sensor in less expensive camcorders is larger than the actual image size. This is so the cam-
era can use electronic stabilizationto compensate for any jiggle or vibration that would otherwise
be captured by the camera. Small gyroscopes in the camera detect the movements and signal the cam-
era’s circuitry. If the movement, for example, shifts the image hitting the sensor to the right, the circuitry
shifts which pixels are being recorded to the right. Note that the pixels do not actually move, but rather
the responsibility each has to capture a certain part of the image moves to a different pixel. More
expensive camcorders make use of optical image stabilization to move the actual image sensor. See
“How Digital Cameras Cure the Shakes,” in Chapter 8.