A video camera takes continuous pictures and generates a signal for display or recording. It captures images by breaking them down into a series of lines. For example, NTSC, the U.S. and Canadian analog standard uses 525 scan lines. Each line is scanned one at a time, and the continuously varying intensities of red, green and blue light across the line are filtered out and converted into a variable signal, which is most often converted to digital.
A Sony high definition video camera.
The video camera, 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; for many years, videotape has been the primary format used for this purpose, but optical disc media, hard disk, and flash memory are all increasingly used. 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.
It is also interesting to see the emergence of pocket video camera using flash memory, they could become the iPod of digital cameras.
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).