The lens is equipped with Sigma's own unique OS (Optical Stabilizer) function. This function uses two sensors inside the lens to detect vertical and horizontal movement of the camera and works by moving an optical image stabilizing lens group to effectively compensate for camera shake. This system offers the use of shutter speeds approximately 4 stops slower. It also automatically detects movement of the camera and compensate for camera shake when shooting moving subjects such as motor sports. Its compact construction has an overall length of 88.5mm (3.5"), maximum diameter of 74mm (2.9") and weight of just 450g/15.9oz (Sigma mount). This lens has a minimum focusing distance of 35cm (13.8") at all focal lengths, and has maximum magnification of 1:3.8, making it ideal for close-up photography. SLD (Special Low Dispersion) glass, a molded glass aspherical lens and two hybrid 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.