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Canon EOS 40D Guide to Digital Photography by David D. Busch

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Categories of Lenses

Lenses can be categorized by their intended purpose—general photography, macro photography, and so forth—or by their focal length. The range of available focal lengths is usually divided into three main groups: wide-angle, normal, and telephoto. Prime lenses fall neatly into one of these classifications. Zooms can overlap designations, with a significant number falling into the catch-all wide-to-telephoto zoom range. This section provides more information about focal length ranges, and how they are used.

Any lens with an equivalent focal length of 10mm to 20mm is said to be an ultra-wide-angle lens; from about 20mm to 40mm (equivalent) is said to be a wide-angle lens. Normal lenses have a focal length roughly equivalent ...

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