This compact high-performance telephoto zoom lens incorporates Sigmas own Optical Stabilizer function. The lens incorporates SLD (Special Low Dispersion) glass in the front lens groups & is equipped with an inner focusing system to provide high image quality throughout the entire zoom range. The incorporation of HSM (Hyper-Sonic Motor) ensures quiet & high-speed auto focus. The OS (Optical Stabilizer) function effectively eliminates the effects of camera shake so subjects can be easily & clearly seen in the viewfinder as well as in the image. It allows the use of shutter speeds up to 4 stops slower than normal for steady, handheld photography. For Sony & Pentax mounts the built-in OS System allows the photographer to see the stabilized image in the viewfinder & can be used as an alternative with cameras having built-in image stabilization. The super multi-layer coating reduces flare & ghosting & provides high contrast images throughout the entire zoom range. This lens has a minimum focusing distance of 43.3 inches throughout the entire zoom range & a maximum magnification ratio of 1:4.5. An inner focusing system eliminates front lens rotation, making it suitable for use with circular polarizing filters.