- br br Best Price Review - Canon EF 100mm f 2.8 Macro USM Lens for Canon SLR Camerasbr br 100mm macro USM lens with f2.8 maximum aperture for Canon SLR camerasbr Secondary diaphragm blocks stray light at f2.8 for increased contrastbr Ultra-sonic monitor provides outstanding autofocusing speed at all distancesbr 3-group floating system for exceptional close-up performance; full-time manual focusbr Measures 3.1 inches in diameter and 4.7 inches long; weighs 21.