4 minute read
Camcorders
Technology
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How camcorders work
Learn how the latest digital video cameras capture and record hi-def footage
Modern digital recorders fundamentally work in the same way as the original analogue camcorders of the Eighties – those bulky, VCR-recording devices wielded on the shoulder. They both comprise a lens, imager and storage medium, but the main differences are that today’s camcorders convert analogue data to a digital form and that the technology as a whole has miniaturised to a far more practical, handheld level.
A camcorder uses a lens to focus patterns of light from a scene onto an imager – a CMOS sensor or charge-coupled device (CCD). The latter is a small semiconductor that houses around half a million photosites – tiny diodes sensitive to light that measure the number of photons that strike it before converting them into an electrical charge. The strength of this charge tells the camcorder during playback how intense the light at that point should be. Colour is recorded by measuring the levels of green, red and blue, because any colour can be replicated with a mix of these three primary shades.
Of course, CCDs in camcorders have to record moving images, so the device must capture multiple frames. To do this, the CCD transfers each frame of video to an extra sensor behind the main imager in a small relay system. This second sensor transmits the electric charges at each of the photosites to the analogue-to-digital converter, while the first layer wipes itself blank, ready to capture the next image.
The latest top-of-the-range camcorders pack an unbelievable amount of technology into a tiny body, relative to the video recorders we started with 30 years ago. The Hitachi Super Hi-Vision, for example, can shoot 33 megapixels (7,580 x 4,320 resolution) at 120 frames per second. That’s 4 billion pixels caught each moment – the same kind of detail seen on an IMAX cinema screen.
Video recorder tech
We take a peek at the technology enabling us to shoot ever-better home movies
Spindle
A small motor can drive the miniDVD on a spindle at around 500 spins a second.
Lens
The lens screws on to the top of the imager and focuses the light on the sensor underneath.
Laser reader
Some older models of camcorders include a laser reader/writer for recording to and reading from miniDVDs.
Curved body
Camcorders can be made shockproof (ie protected from falls) by padding the corners and building a solid frame with a curved shape that’s inherently strong.
Materials
Typically made out of light but durable plastic, some specialised camcorders (like the GoPro HERO3) are also sealed in order to make them waterproof.
JVC launches an alternative standard to the Betamax video player: the VHS format (right).
DID YOU KNOW? Jerome Lemelson tried to patent the camcorder in 1977, but his idea was rejected for being too unrealistic!
Analogue vs digital
The main difference between a digital and analogue camcorder is the way data is recorded. Analogue camcorders record it as magnetic patterns, usually on magnetic VHS tape. The two main problems with this is that analogue recording takes up a lot of physical space in the form of bulky cassette tapes, a lot of logical space on a hard disk drive and analogue data can also ‘fade’ each time it’s copied, as the original recording signal isn’t replicated precisely. Digital camcorders, on the other hand, add an analogue-todigital converter stage to the end of the capture process, transforming the analogue signal into a series of binary 1s and 0s. Digitising the data this way allows it to be compressed into a much smaller logical volume on a memory card or solid-state drive. Data can also be reproduced exactly, so it doesn’t suffer from degradation over time like analogue.
The Panasonic HDC-TM300 uses three full-HD MOS sensors, which between them can capture a total 9,150,000 pixels
LCD display
Since the earlyNineties, a small LCD display has replaced the original viewfinder and become the standard.
Logic board
This contains all the chips for processing the image data, converting it into a digital format and sending it to the storage device.
Image sensor
Moving images are captured at this point, by a CCD or CMOS sensor.
CMOS battery
Maintains power to the CMOS chip that stores basic data such as date and time, even when the camcorder is turned off.
Making sense of sensors
A CMOS (complementary metaloxide-semiconductor) sensor is an image sensor that often takes the place of a CCD (charge-coupled device) in mobile phones, webcams and DSLR cameras. CMOS sensors use tiny transistors located at each pixel to read each point individually. The transistors take the electron charge that has been converted from the captured point of light and amplify it, before transferring it across wires.
As CMOS sensors combine image processing and capture on the same device, it generally uses less power than a CCD, has less lag and requires fewer costly processes during manufacture. For these reasons, CMOS sensors are common in mobile phone cameras where cheaper, powerefficient components are vital. As the wires in CMOS sensors make them prone to image noise, they tend to have lower-quality results than CCDs, so the latter are often used in higher-end imaging tech.
