This 20mm is a Super wide-angle lens with a large aperture of f/1.8 and angle of view 94.5°. It has Macro focusing capability with a minimum focusing distance of just 7.9", for a reproduction ratio of 1:4. The 9-bladed iris diaphragm obtains beautiful out of focus image characteristics. Aspherical lens elements in the front & rear lens groups minimize distortion, spherical aberration and astigmatisms. The lens has non-vignetting optical construction in order to obtain adequate peripheral brightness with wide apertures-especially desirable for digital cameras. The lens incorporates a rear focus system eliminating front lens rotation. The focusing ring does not rotate during autofocus yet provides adequate focusing torque of the focusing ring during manual focusing of the lens. The lens materials used in this new lens are lead and arsenic free ecological glass.