| What type of camera do I need for video capture? |
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| The type and quality of camera you require depends on the application. In general, most home hobbyists will opt for an inexpensive one-chip CCD colour camera, while high-end video applications require a three- chip colour CCD or tube camera. Most scientific work requires the high definition grayscale of a monochrome CCD or tube camera. CCD vs. Tubes Charge Coupled Device (CCD) cameras are a solid-state, inexpensive and durable alternative. The same technology as is incorporated into camcorders is used in stand-alone CCD video cameras. CCD's consist of an array of light-sensitive material, which produces an electrical signal when struck with a light photon. As light photons continually stream through the lens and strike the CCD, they produce different voltages in corresponding CCD elements. By sampling the voltage generated at each element, an analog raster representation of light intensity is collected. This produces a grayscale representation of the sampled light image, where the maximum voltage corresponds to white, and the minimum corresponds to black. CCD's suffer from black noise (noise generated from an element even when no light photons are striking it) and relatively low light sensitivity, though newer CCD's are improving. CCD's have the advantage of low cost and high durability. Tube cameras use older tube technology instead of solid-state silicon. They are very light sensitive, and so are useful for low- light applications. In general, most tube cameras are used when CCD technology in inadequate. They are more expensive than CCD's and are more easily damaged by excessive light exposure. Colour CCD Two varieties of colour CCD's are available; one and three chip implementations. A three chip CCD uses three discrete CCD arrays, each with a colour filter in front of it: red, green or blue. Each CCD is sampled in a raster fashion, the same as for the grayscale device, above, and the result is a colour analog signal. Because they require three discrete CCD's, the three chip models are more expensive than one chip models and provide better colour reproduction. The latter use one CCD, and no colour filters. They consider the energy of the incoming photons, which determines their colour, to produce a red, green and blue value for each CCD element in the array. While cheaper, colour reproduction of one chip CCD's is inferior to three chip. Digital Cameras Although expensive and used less frequently than analog video cameras, digital cameras have the advantage of not requiring dedicated frame capture hardware in the computer. They are based on the same CCD technology as is described above. An example of a digital camera is the IndyCam which come with SGI Indy workstations. Also, hand-held portable digital cameras are available which can download images to your computer. |
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