Canon EF 28mm f/2.8 IS USM Wide Angle Lens - Fixed Focal length and maximum aperture: 28mm 1:2.8 Lens construction: 9 elements in 7 groups Diagonal angle of view: 75 Degree Rear focusing system with USM focus adjustment Closest focusing distance: 0.23m/0.75 ft..Please be advised that when EF 28mm f/2.8 IS USM is used with EOS-1D Mark IV, the firmware of the camera should be updated to version 1.1.1 or later. The update helps to optimize the exposure accuracy Lens not zoomable