The Sigma 20mm f/1.8 EX DG ASPHERICAL RF is a Wide angle lens with large aperture and superior peripheral brightness This super-wide-angle lens is ensured minimal light-fall-off with superior peripheral brightness. The iris diaphragm has 9 diaphragm blades to obtain beautiful out of focus images in the foreground and background. This is an ideal DG lens optimized Digital SLR camera Minimum focus distance of 20cm The minimum focusing distance of this lens is 20cm and it has maximum magnification of 1:4 with fast F 1.8 maximum aperture. The minimum focusing distance of 20cm and 94.5 degree angle of view allow close up photography surrounding the photographic subject.
Handling The lens incorporates Dual-Focus (DF) mechanism. It is easy to hold the lens, since the focusing ring does not rotate during auto-focus, yet it provides adequate focusing torque of the focusing ring during manual focusing of the lens. The rear focus system eliminates the need for the front of the lens to rotate, thus allowing the use of a ""Petal-type hood"", which is superior light blocking effect. Incorporated aspherical lenses The use of aspherical lens elements in both of the front and rear lens groups effectively compensates for distortion, spherical aberration and astigmatism.