CANON 100MM F/2.8 MACRO USM EF From the Manufacturer: Bring small things into full-sized view with the Canon EF 100mm macro USM lens. Macro lenses can uncover detail that would be impossible to detect by the eye and give new perspective to extremely minute subjects such as insects or the petals of a small flower, and this lens is no exception. The lens offers such features as a three-group floating system for exceptional close-up performance; a secondary diaphragm that blocks stray light at f/2.8, which increases contrast when shooting wide open; a ultra-sonic monitor (USM) that provides outstanding autofocusing speed at all focusing distances; a wide manual focusing ring with smooth action; and full-time manual focus even in AF mode. Focal length: 100mm Maximum aperture: 1:2.8 Lens construction: 12 elements in 8 groups Diagonal angle of view: 24 degrees Focus adjustment: Inner focusing system with USM Closest focusing distance: 1 foot (film plane to subject) Filter size: 58mm Dimensions: 3.1 inches in diameter, 4.7 inches long Weight: 21.1 ounces.