History of Photography-09
Digital camerasDigital cameras differ from their analog predecessors primarily in that they do not use film, but capture and save photographs on digital memory cards or internal storage instead. Their low operating costs have relegated chemical cameras to niche markets. Digital cameras now include wireless communication capabilities (for example Wi-Fi or Bluetooth) to transfer, print or share photos, and are commonly found on mobile phones.
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. Early spy satellites used the extremely complex and expensive method of de-orbit and airborne retrieval of film canisters. Technology was pushed to skip these steps through the use of in-satellite developing and electronic scanning of the film for direct transmission to the ground. The amount of film was still a major limitation, and this was overcome and greatly simplified by the push to develop an electronic image capturing array that could be used instead of film. The first electronic imaging satellite was the KH-11 launched by the NRO in late 1976. It had a charge-coupled device (CCD) array with a resolution of 800 x 800 pixels (0.64 megapixels). At Philips Labs in New York, Edward Stupp, Pieter Cath and Zsolt Szilagyi filed for a patent on "All Solid State Radiation Imagers" on 6 September 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 10 November 1970. Texas Instruments engineer Willis Adcock designed a filmless camera that was not digital 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 compact 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.
Analog electronic cameras
Handheld electronic cameras, in the sense of a device meant to be carried and used like a handheld film camera, appeared in 1981 with the demonstration of the Sony Mavica (Magnetic Video Camera). This is not to be confused with the later cameras by Sony that also bore the Mavica name. This was an analog camera, in that it recorded pixel signals continuously, as videotape machines did, without converting them to discrete levels; it recorded television-like signals to a 2 × 2 inch "video floppy". In essence it was a video movie camera that recorded single frames, 50 per disk in field mode and 25 per disk in frame mode. The image quality was considered equal to that of then-current televisions.
Abu Kalam Shamsuddin