With a maximum angle of view of 104º, this lens uses a large aspherical lens for element 1 and another aspherical lens for element 15. They correct distortion and greatly improve peripheral resolution. A gelatin filter holder on the rear of the lens accepts up to three pre-cut gel filters. The lens also accepts screw-on filters (77mm). Focal Length & Maximum Aperture: 17-35mm 1:2.8 Lens Construction: 15 elements in 10 groups Diagonal Angle of View: 104º - 63º Focus Adjustment: Inner focusing system with USM Closest Focusing Distance: 0.42m / 1.4ft. Zoom System: Rotating type Filter Size: 77mm Max. Diameter x Length, Weight: 3.3" x 3.8", 1.2 lb. / 83.5 x 95.7mm, 545g