Autofocus lens for macro photography up to life-size magnification (1x). Internal focusing allows for a long working distance of 149mm at 1x. A 3-group floating system provides excellent sharpness at all focusing distances. USM motor for silent and fast autofocus, with manual focus also permanently available. Features - Focal length: 100mm - Maximum aperture: 1:2.8 - Optical construction comprising 12 elements in 8 groups - Entirely new optical design, with a three-group floating system for exceptional macro performance - First lens in its class to incorporate internal focusing. The lens length never changes, even at life-size magnification! - A secondary diaphragm blocks stray light at f/2.8, increasing contrast when shooting at full aperture - The ultrasonic motor offers exceptional AF speed at all focusing distances - Large smooth-action manual focus ring, and permanent manual focus even in AF mode