Sigma 20mm F1.8 EX DG Aspherical RF
Sigma 20mm F1.8 EX DG Aspherical RFThis super-wide-angle lens exhibits minimal light-fall-off with superior peripheral brightness. The iris diaphragm has 9 blades to obtain beautiful out of focus images in the foreground and background. This is an ideal DG lens optimized Digital SLR camera.
The minimum focusing distance of this lens is 20cm (7.9 inch) and it has maximum magnification of 1:4 with fast F1.8 maximum aperture.
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".
The use of aspherical lens elements in both of the front and rear lens groups effectively compensates for distortion, spherical aberration and astigmatism.