DESC: Autofocus lens for macro photography up to life-size (1x) magnification. Inner focusing affords a long working distance of 5.9in. (149mm) at 1x. A 3-group floating system results in excellent delineation at all focusing distances. Ring USM for silent and high-speed AF, and full-time manual focusing also provided. The optional Tripod Mount Ring (B) B (with adapter) enables the lens to be rotated for vertical or horizontal framing.