Video_camera

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. Such cameras generally offer extremely fine-grained manual control for the camera operator, often to the exclusion of automated operation.
• 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 can be considered a type of CCTV camera.
• Digital cameras which convert the signal directly to a digital output; such cameras are often extremely small, even smaller than CCTV security cameras, and are often used as webcams or optimized for still-camera use. 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 or for other digital input, though such units may need to pass their output through an analog-to-digital converter in order to store the output or 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).

Common issues with video camera systems

Some people find video to have a grainy and less desirable look than film, and indeed a great many music videos have traditionally been shot on film rather than videotape. With the rise of digital video, however, it has become practical to emulate the "film look" using progressive scan and improved telecine techniques. Many television shows (and even theatrical movies) which would in the past have been shot on film are now done using video, and the capability to do this exists even in some high-end consumer/prosumer equipment.

When imaging a separate video source (i.e. a computer monitor or television, usually one that produces a scanned image), there is often substantial visual artifacting (rolling bars on the monitor screen, for example) generated by differing timing signals between the monitor and the camera. This is generally only an issue with CRT displays and is not common on non-scanning displays such as LCD units.

Similar to audio equipment, video cameras are subject to optical feedback effects. This has sometimes been used to create special video effects (most notably the titles of the first seasons of Doctor Who, ultimately refined into the Tom Baker-era "time vortex" graphic). A more common effect is sometimes referred to as an "endless hallway", that is, an infinite regression consisting of the screen showing pictures of itself; certain stroboscopic effects (shown in a montage in Douglas Hofstadter\'s Gödel, Escher, Bach: An Eternal Golden Braid) are also possible when the camera creating the feedback is in motion relative to the screen.

See also

Look up Video camera in
Wiktionary, the free dictionary.

• Video camera tube
• 3CCD
• Connection technologies
  • Composite video, Component video, and S-video
  • SDI and SDTI
  • FireWire
  • USB
  • DVI and HDMI

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