SIGMA 28-70mm f2.8 EX Aspherical DF is one of several EX-Series lenses. It combines a fast, constant f2.8 maximum aperture with a popular range of focal lengths from 28mm wide-angle to 70mm medium range telephoto with an upgraded design. It is the world's smallest 28-70mm f2.8 zoom lens. The lens also incorporates a dual focus mechanism. It is easy to hold the lens, since the focusing ring does not rotate during auto-focusing and yet provides adequate focusing torque of the focusing ring during manual focusing of the lens. Helical focus system of the lens eliminates front lens rotation, thus allowing the use of a Perfect Hood and easy to use polarizing filters. It incorporates 2 aspherical lenses in the front and rear lens groups, provides high performance and superior optical quality. Minimum focusing distance is 40cm/15.7inches at all focal lengths. Sigma 28-70mm f2.8 EX Aspherical DF is equipped with a Perfect Hood to prevent extraneous harmful light for image quality. The lens materials used in this new lens are lead and arsenic free ecological glass.