Optics  12 elements in 9 groups, including three aspherics and one of UD glass. UD glass is the same as Nikon's ED glass, which helps reduce color fringing.    Focal Length  17-40mm.    Used on a 1.3x camera it gives angles of view similar to what a 21-50mm lens would give on a 35mm film camera.    Diaphragm  7 mostly straight blades stopping down to f/22.    Close Focus  11"" (0.28m) from the image plane (the back of the camera)    Weight  16.705 oz. (473.6 g), measured, naked. (4.440 ox, 125.85g less than the 16-35mm L.