A schematic diagram taken from a
Canon camcorder manual
To learn how a camcorder works we need a basic introduction to electronics. Unlike a film camera, a camcorder uses a CCD to capture an image. This camcorder guide is not meant to be a full-blown course in electronics so well keep things simple.
CCD stands for Charged Coupled Device, and its an electronic sensor that captures light onto its face. The camcorders iris determines the intensity of the light hitting the lens. It is the CCD, however, that measures the intensity of the light striking the face of the chip as well as the color of the light.
Through this process, an image is
rendered. Some camcorders have 3 CCDs - one for each of the primary colors, red,
blue and green. Each of these chips does its own job of color separation. These
camcorders produce richer colors, but the added CCDs mean the camera is more
complex, and more expensive.
The Concept of Video Signals
After the light hits the CCD, a video signal is generated. Well give a brief introduction to the concept of video signals in this camcorder guide.
If you know anything about television, you know that television creates a video image by using what are called scan lines. A camcorder works the same way, except these lines are called fields. Two sets of fields make up the camcorders image on the CCD. These fields are divided into odd and even numbered scan lines.
As the scanning takes place, each field passes to a second layer behind the CCD, known as the sensor layer. The sensor layer records each electric charge that makes up that field and then writes that information to the tape.
With digital camcorders, there is
an added twist on that last step. A special converter inside the camcorder
converts that electrical information into digital signals made up of bytes of
Features to Enhance Video Signals
You might think by now you really know how a camcorder works, but theres more! Nowadays camcordersespecially the digital ones that are all the rage - have additional features and effects. These camcorders have special built-in electronics that enable the user to enhance the video signal.
One important feature is called 'gain'. If youve ever shot in a low light setting, you notice that your shots are dark and grainy. With your electronic gain, you can basically 'brighten up' those dark pixels to make the picture brighter than it would normally be. It wont be as good as having a flood of lights, but it helps!
Also, special electronics in the
camcorder allow you to apply effects like black and white, sepia, fade, and so
forth. Electronics makes all of these effects possible by taking the video
signal and enhancing and manipulating it. Afterwards the processed video signal
is then sent to tape.
The process by which the video signal is recorded to tape is called helical scanning. The phrase sounds a bit arcane, but its worth explaining. Video information is not stored as a straight line (linear). Rather, its placed down at an angle, each frame stored on tape at a slant.
Without getting too deep into the technical reason for this, the basic idea is to save space on tape. Since video has both audio and video information, if it were all stored as one consecutive line, you would need a lot of tape to store it!
By recording at a slant and then
stacking the stripes together, you get more information in less space. The
rotating tape drum has two heads that read or write to tape. If youre in
standby mode, they just rub over the tape without recording anything. But they
make a rather annoying humming sound. Eventually theyll stop spinning if you
havent recorded anything for awhile so as not to wear out the heads and the
Understanding the Playback Mode
The final step in understanding how a camcorder works has to do with the playback mode. You can play your videotape in a VCR, or you can use it using the built-in VCR that comes with your camcorder. Either way, the basic process is the same. In fact, playback is basically the recording process in reverse.
Lets begin with the video signal. The VCR amplifies the original signal and then converts it into a composite video signal. That signal could go directly to your camcorder (letting you view the video in the viewfinder), or it could go to another outside source, like your television.
In fact, once you have a composite
signal, you can connect it to many different sources. With the audio signal, it
too is amplified and then sent to a different output. Thus you wind up with
output for both audio and video. You might recall that your regular VCR has two
outputs for audio and video as well.
Whew! That was quite a dive into studying how a camcorder works. We have probably skimmed the surface of some points to keep things as simple as possible.
Im sure you have a better understanding of what a marvel of modern technology a camcorder really is. It requires precision optics, mechanical and electronic engineering and miniaturized circuitry to create a device like this.
I think you understand that building the camcorder required overcoming some design hurdles in the process. Engineers had to think of ingenious methods (like helical scanning) of getting the camcorder to pull an amazing amount of performance out of such a tiny unit!
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