Covering the most frequently used focal lengths, from mid to long-range telephoto, this one convenient lens lets you handle an unprecedented range of subjects from landscapes to fast action sports. Sigma's advanced design incorporates a 5-group zoom system to achieve sharp, high contrast results throughout the entire zoom range. Three SLD glass elements eliminate the secondary spectra effect normally associated with telephotos. And the rear focus system keeps the front lens from rotating, giving you easier use of polarizing filters. A convenient built-in rotary tripod mount eliminates vibration during shutter release.