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SLD (Special Low Dispersion) glass for high image quality.
This lens uses two pieces of SLD glass elements in the front lens group and another two in the rear group for excellent correction of chromatic aberration. High optic performance is demonstrated throughout the entire zoom range.

HSM (Hyper Sonic Motor) ensures a quiet, high-speed AF
The AF drive for Sigma SA, Canon and Nikon cameras is equipped with a silent, responsive and high speed HSM (Hyper Sonic Motor), which also provides full-time manual focus function.

Inner focusing and inner zooming systems
This lens incorporates an internal focusing system, which eliminates front lens rotation, allowing the use of a Petal-type Hood and more convenient to use of circular polarizing filter. Since focusing and zooming do not change its overall length, this lens is easy to hold and use.

APO lens
The use of an Apochromatic design and 4 SLD (The Special Low Dispersion) glass elements (two SLD glass elements are utilized in the front lens group and two in the rear group) provide for full correction of chromatic aberration and a high level of optical performance.

APO Tele-Converter EX (optional)
High-speed focusing is possible when this lens is used with dedicated APO EX tele-converters (1.4x and 2x). With the optional APO tele-converter 1.4x EX, it works as AF zoom lens from 140mm to 420mm F5.6. With APO tele-converter 2.0x EX, it works as a manual focus zoom lens from 200mm to 600mm F8.
It is possible to use AE (Automatic Exposure) function, even EX Tele-converters are attached to the lens.