Sigma broadened out its lens lineup at CES, announcing a fast prime and a standard zoom in a range of mounts that should give anyone looking for third party lenses options to consider. The fast prime is a 50mm ƒ/1.4 DG HSM 'Art' lens. 'DG' is the equivalent of Nikon's FX format or Canon's EF lenses, meaning that they are designed for use with both full-frame and APS-C sensor cameras. HSM is hyper sonic motor, giving it fast and quiet auto-focusing capability. The 'Art' line of lenses are intended to deliver 'high level artisitic expression' to photographers.
This lens is an upgrade on Sigma's previous 50mm ƒ/1.4, which was released in 2008. It comes in Canon, Nikon, Sigma, and Sony mounts. There's no price on the lens yet, but it'll be interesting to compare it against Canon's, Nikon's, and Sony's equivalents.
Sigma's other new lens is the 18-200mm ƒ/3.5-6.3 DC Macro OS HSM, in the 'Contemporary' line. This is a DC lens, which makes it optimised for APS-C sensor cameras, much like Canon's EF-S and Nikon's DX-format lenses. If you tried to put it on a full-frame camera you'd end up with a vignette. In the equivalent of 35mm format, this lens has a focal length range of 27 to 300mm.
This version has been developed to be smaller and lighter than its predecessor, the macro function gives it a minimum focusing distance of 39cm, and there's optical stabilisation (in the Canon and Nikon mounts) to help in lower light conditions.
This lens is available in Canon, Nikon, Pentax, Sigma, and Sony mounts. There's no direct Pentax equivalent for this lens and the Canon and Nikon options have superior maximum apertures at their longest focal lengths (ƒ/5.6 as opposed to ƒ/6.3), so it'll be interesting to see how they compare in both price and performance.