A digital camera (or digicam for short) is a camera that takes video or still photographs, or both, digitally by recording images via an electronic image sensor.
Front and back of a Canon PowerShot A95.

Many compact digital still cameras can record sound and moving video as well as still photographs. In the Western market, digital cameras outsell their 35 mm film counterparts.

Digital cameras can do things film cameras cannot: displaying images on a screen immediately after they are recorded, storing thousands of images on a single small memory device, recording video with sound, and deleting images to free storage space. Some can crop pictures and perform other elementary image editing. Fundamentally they operate in the same manner as film cameras, typically using a lens with a variable diaphragm to focus light onto an image pickup device. The combination of the diaphragm and a shutter mechanism is used to admit the correct amount of light to the imager, just as with film; the only difference is that the image pickup device is electronic rather than chemical.

Digital cameras are incorporated into many devices ranging from PDAs and mobile phones (called camera phones) to vehicles. The Hubble Space Telescope and other astronomical devices are essentially specialised digital cameras.

Wednesday, October 28, 2009

History

Early development

The concept of digitizing images on scanners, and the concept of digitizing video signals, predate the concept of making still pictures by digitizing signals from an array of discrete sensor elements. Eugene F. Lally of the Jet Propulsion Laboratory described a mosaic photosensor for use as a star sensor for measuring the altitude of a spacecraft at a 1961 space conference. At Philips Labs. in NY Edward Stupp, Pieter Cath and Zsolt Szilagyi filed for a patent on "All Solid State Radiation Imagers" on Sept. 6, 1968 and constructed a flat screen target for receiving and storing an optical image on a matrix composed of an array of photodiodes connected to a capacitor to form an array of two terminal devices connected in rows and columns. Their US patent was granted on Nov. 10, 1970. Texas Instruments engineer Willis Adcock designed a filmless camera and applied for a patent in 1972, but it is not known whether it was ever built. The first recorded attempt at building a digital camera was in 1975 by Steven Sasson, an engineer at Eastman Kodak. It used the then-new solid-state CCD image sensor chips developed by Fairchild Semiconductor in 1973. The camera weighed 8 pounds (3.6 kg), recorded black and white images to a cassette tape, had a resolution of 0.01 megapixels (10,000 pixels), and took 23 seconds to capture its first image in December 1975. The prototype camera was a technical exercise, not intended for production.
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