Canon EF 400mm f/5.6L USM Super Telephoto Lens for Canon SLR Cameras Lens construction: 7 elements in 6 groups Diagonal Angle of View: 6 10' .Fluorite and Ultra-low Dispersion-glass; internal focusing; full-time manual focus Closest Focusing Distance: 35m / 115 ft Focal Length &amp; Maximum Aperture: 400mm 1:56 Filter size: 77mm