Sigma 24mm f1.8 EX DG Aspherical Macro is one of the EX Series lenses. This lens has a fast F1.8 maximum aperture with macro focusing capability of minimum focusing down to 18cm/7.1inches (reproduction ratio 1:2.7). The iris diaphragm has 9 diaphragm blades to obtain beautiful out of focus image. It incorporates the floating focus system and uses two aspherical lens elements for minimizing distortion and spherical aberration and astigmatism. Internal focus system eliminates front lens rotation, thus allowing the use of a Perfect Hood and the easy use of polarizing filters. The lens incorporates non-vignetting optical construction, in order to obtain adequate peripheral brightness even at open aperture. This is desirable for digital cameras. The lens also incorporates dual-focus mechanism. It is easy to hold the lens, since focusing ring does not rotate during auto-focus, and yet it provides adequate focusing torque of the focusing ring during manual focusing of the lens. The lens materials used in this lens are lead and arsenic free ecological glass.