Sensor:

Typical sensor size of 3, 4, and 5 megapixel digital compact cameras	Typical sensor size of 6 megapixel digital SLRs

This diagram shows the typical sensor sizes compared to 35mm film. The sensor sizes of digital SLRs are typically 40% to 100% of the surface of 35mm film. Digital compact cameras have substantially smaller sensors offering a similar number of pixels. As a consequence, the pixels are much smaller, which is a key reason for the image quality difference, especially in terms of noise and dynamic range.
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History of Digital Photography:

The very first forms of photography date back to the early 19th century when America's history was captured on film during the Civil War. Since then many advancements have been made in the world of photography. One of the newest advancements in the field was the birth of digital photography. In 1963 when a student at Stanford University invented a videodisk camera that could take a photograph and store the image on a disk for several minutes this would be the precursor to digital photography. With this new form of taking photographs digitally and storing the image to a disk, photography would become less time consuming and a whole new chapter would open to future photographers. In the mid 70s Kodak began to work on filmless technologies. In the mid 80s with the release of the compact disc digital technology was vastly increasing. By 1990 the first digital camera hit shelves for commercial sales. These would be the first steps into a new digital world, and pave the way for many things to come.

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-Minnie