If you have your eye on the Canon EOS 30D, this could be the perfect all-around lens for it. Its focal-length range is equivalent to 27-88mm, with a fast, constant f/2.8 maximum aperture throughout. Optical quality is comparable to that of Canon's premium L-series lenses for full-frame cameras (only with a more manageable price), and is maximized by built-in optical image stabilization. About $1,180.
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