Images produced by digital cameras now rival the quality of our finest photographic film stocks. But the nature of a digital image shares almost nothing in common with the analog image captured in a film emulsion.
An image captured in film is an incredibly complex physical object that has a life of its own, and can be interpreted directly by inspection with the human eye. A digital image, on the other hand, is an electronic representation of a scene – a sequence of numbers specifying red, green, and blue light intensities that requires some form of software to render it into a visual form that can be displayed on a suitable imaging device, like a photo-printer.
When an image is captured digitally, it is done with a mosaic of light-sensitive electronic pixels. These pixels are actually independent square-shaped photodiodes which are arranged in the form of a large tiled surface. Well, large from the point of view of a single pixel, since if we were to enlarge the pixel to the size of a kitchen floor tile, then the area covered by the entire image sensor would be about the same as that of a football stadium.
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