The Sigma 24-70mm f2.8 EX Aspherical DG DF is one of several products to be introduced at PMA 2001 by Sigma Corporation of Japan (2-3-15, lwado-Minami, Komae-shi, Tokyo) This lens covers focal lengths from 24mm ultra wide angle to 70mm medium telephoto and provides a large f2.8 aperture at all focal lengths. Its design employs three (3) aspherical lens elements to minimize spherical aberration, astigmatism and sagittal comma flare. The use of two (2) SLD (The Special Low Dispersion) glass elements results in excellent correction of chromatic aberration and provides a high level of optical performance and 24-70rnm F2.8 EX ASPHERICAL DG DF has high contrast and resolution. The lens also incorporates Dual Focus mechanism. It is easy to hold the lens, since the focusing ring does not rotate during auto focusing, and yet provides a wide focus ring for easy to use manual focus. Since the front of the lens does not rotate, it allows the use of a flower shaped "Perfect Hood" and facilities the use of polarizing filters. The lens materials used in this lens are lead and arsenic free ecological glass.