Sigma 200-500mm APO lens: It covers the widely used 200 to 500mm focal length range, and maintains its fast F2.8 aperture over the entire zoom range. Four SLD glass elements provide excellent correction for all types of aberrations and produce a high level of optical performance throughout the entire zoom range. Shooting distance and focal length can be viewed on the lens' LCD panel, which is an additional convenience for the photographer. A filter can be inserted towards the rear of the lens, and a circular polarizing filter can be used with its ingenious rotation mechanism. About Sigma After nearly 40 years of pioneering new and better ways to capture and portray the ordinary - and extraordinary - Sigma is still creating new avenues of expression with innovative designs and enhancements in zoom and non-zoom lenses and single lens reflex cameras. As one of the first manufacturers to successfully introduce the interchangeable lens, Sigma's well-earned reputation for originality, innovation and leadership is your guarantee of the world's most advanced line of photographic products. Products you and millions of photographers worldwide turn to when quality, reliability and professional results count most.