Video Cameras
A video camera is a
camera
used for electronic motion picture acquisition, initially developed by the
television industry but now common in other applications as well. The earliest
video cameras were those of John Logie Baird, based on the electromechanical
Nipkow disk and used by the BBC in experimental broadcasts through the 1930s.
All-electronic designs based on the cathode ray tube, such as Vladimir
Zworykin's Iconoscope and Philo T. Farnsworth's Image Dissector, supplanted the
Baird system by the 1940s and remained in wide use until the 1980s, when
cameras
based on solid-state image sensors such as CCDs (and later CMOS active pixel
sensors) eliminated common problems with tube technologies such as burn-in and
made digital video workflow practical.
Video cameras are used primarily in two modes. The first, characteristic of much
early
television, is what might be called a live broadcast, where the
camera
feeds real time images directly to a
screen for
immediate observation; in addition to live
television production, such usage is
characteristic of security, military/tactical, and industrial operations where
surreptitious or remote viewing is required. The second is to have the images
recorded to a
storage device for archiving or further processing;
videotape
is traditional for this purpose, but optical disc media,
hard disk,
and flash memory
are all used as well. Recorded video is used not only in
television and film
production, but also surveillance and monitoring tasks where unattended
recording of a situation is required for later analysis.
Modern video cameras have numerous designs and uses, not all of which resemble
the early
television cameras.
Professional video cameras, such as those used in
television and sometimes film
production; these may be studio-based or mobile.
Camcorders,
which combine a camera and a VCR or other
recording device in one unit; these
are mobile, and are widely used for
television production, home movies,
electronic news gathering (including citizen journalism), and similar
applications.
Closed-circuit television cameras, generally used for
security, surveillance, and/or monitoring purposes. Such
cameras are
designed to be small, easily hidden, and able to operate unattended; those used
in industrial or scientific settings are often meant for use in environments
that are normally inaccessible or uncomfortable for humans, and are therefore
hardened for such hostile environments (e.g. radiation, high heat, or toxic
chemical exposure).
Webcams, which provide digital video feeds for
computer systems
and networks,
and other small
digital
cameras; such
cameras
are often extremely small, even smaller than
CCTV security cameras. These cameras are sometimes incorporated directly
into computer or communications hardware, particularly mobile phones, PDAs, and
some models of laptop computer. Larger video cameras (especially
camcorders and
CCTV cameras) can also be used as
webcams, though many such units may need to pass their output through an
analog-to-digital converter in order to send it to a wider
network.
Special systems, like those used for scientific research, e.g. on board a
satellite or a spaceprobe, or in artificial intelligence and robotics research.
Such cameras are often tuned for non-visible light such as infrared (for night
vision and heat sensing) or X-ray (for medical and astronomical use).
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