Photography is the process of making pictures by means of the action of capturing light on a film. Light patterns reflected or emitted from objects are recorded onto a sensitive medium or storage chip through a timed exposure. The process is done through mechanical, chemical or digital devices known as cameras.

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PhotographyThe word comes from the Greek words φως phos ("light"), and γραφις graphis ("stylus", "paintbrush") or γραφη graphê, together meaning "drawing with light" or "representation by means of lines" or "drawing." Traditionally the product of photography has been called a photograph. The term photo is an abbreviation; many people also call them pictures. In digital photography, the term image has begun to replace photograph.

Digital photography
Traditional photography was a considerable burden for photographers working at remote locations (such as press correspondents) without access to processing facilities. With increased competition from television there was pressure to deliver their images to newspapers with greater speed. Photo-journalists at remote locations would carry a miniature photo lab with them and some means of transmitting their images down the telephone line. In 1981 Sony unveiled the first consumer camera to use a CCD for imaging, and which required no film -- the Sony Mavica. While the Mavica did save images to disk, the images themselves were displayed on television, and therefore the camera could not be considered fully digital. In 1990, Kodak unveiled the DCS 100, the first commercially available digital camera. Its cost precluded any use other than photojournalism and professional applications, but commercial digital photography was born.

Digital imaging uses an electronic sensor such as a charge-coupled device to record the image as a set of electronic data rather than as chemical changes on film. Some other devices, such as cell phones, now include digital imaging features. Even though there are no chemical processes, a digital camera captures a frame of whatever it happens to be pointed at, which can be viewed later.

Although digital imaging is conceptually no different from ordinary chemical photography, it has certain distinctions. The primary difference lies in that photography inherently resists manipulation due to the fact that it is an analog process involving film, optics and photographic paper, while digital imaging is a highly manipulative medium since it is purely digital from the beginning. This difference allows for a degree of image post-processing which is comparatively difficult in photography, and thus the distinction has less to do with visual dissimilarities, and far more to do with their quite different communicative potentials and applications. Another basic difference is that at no point in the process is the image truly photographic, or etched by light, as in the chemical processes used to make negatives and prints. It is at first an interpretation by the camera of light intensities detected by a grid of sensors. It only becomes a viewable image only after being translated and reproduced on a display or printing device.

from : en.wikipedia.org