Announced at PMA 2009, the Sigma 18-50mm f/2.8-4.5 DC OS HSM (at left in above photo) is a welcomed addition to its ever-growing line-up of crop-format lenses.

Two features really make this lens stand out.  Optical stabilization helps reduce camera-shake induced blur and allows the steady-handed photographer to use slower shutter speeds than would otherwise be possible when shooting hand held.  Sigma’s hypersonic focusing motor is known for its speed and, in my experience, rivals the real world use of Canon USM-equipped lenses of similar max aperture ranges.

The Sigma 18-50mm f/2.8-4.5 DC OS HSM will be available in Sigma, Canon, Nikon, Sony and Pentax mounts.

More details from Sigma’s press release below.

The Sigma Corporation is pleased to announce the new SIGMA 18-50mm F2.8-4.5 DC OS HSM. This large aperture standard zoom lens incorporates Sigma’s original Optical Stabilisation function. This lens offers a large aperture of F2.8 at 18mm wide angle. This large aperture and anti-shale function is ideal for indoor photography and in low lighting condition.

For Sony and Pentax mount, the built-in OS function of this lens can be used even if the camera body is equipped with an anti-shake function. As compensation for camera shake is visible in the view finder, the photographer can easily check for accurate focus and ensure there is no subject movement.

Two SLD (Special Low Dispersion) glass elements and three aspherical lenses provide excellent correction for all types of aberrations. The Super Multi-Layer Coating reduces flare and ghosting. High image quality is assured throughout the entire zoom range. The lens design incorporates inner focusing and inner zooming systems.

The overall length of the lens does not change during focusing and zooming, ensuring convenient handling. This lens has a minimum focusing distance of 30cm (11.8 inches) throughout the entire zoom range and a maximum magnification ratio of 1:4.1. The incorporation of HSM (Hyper Sonic Motor) ensures a quiet and high speed AF.

* Vignetting will occur if the lens is used with 35mm SLR cameras or digital cameras with image sensors larger than APS-C size.