A revolutionary, ultra-high-magnification zoom lens offering the highest magnification of any interchangeable zoom lens for SLR cameras available at the time. This lens enables hand-held shooting from wide-angle 35mm to super-telephoto 350mm. The optical system features a six lens group construction with five movable lens groups, achieving a high zoom magnification in a lens nearly as compact as the EF 70-200mm f/2.8L. Two UD (Ultra-low Dispersion) glass lens elements (2nd and 3rd) in the first lens group thoroughly eliminate chromatic aberrations at telephoto focal length, realizing the high image quality befitting an L series lens. The rear focusing system drives the small, light-weight 6th lens group by a ring USM (Ultrasonic Motor), enabling quiet, high-speed AF and full-time manual focusing. Shooting at a minimum focusing distance of approx. 0.6m is possible at any focal length from 35mm to 135mm, with a maximum macro magnification of 0.25X obtained at 135mm position. Operation of the lens is fast and smooth with its linear zoom system design, wide manual focusing ring, and highly-efficient, petal-shaped lens hood.