The Sigma 50mm f/1.4 DG HSM (above) is the latest product in Sigma's "Art" line that was originally announced in 2012.
Comprising 13 elements in 8 groups, the complex optical design has been tailored with Special Low Dispersion and aspherical glass elements to minimise a multitude of optical aberrations such as sagittal coma flare (concentric flare), axial chromatic aberration, flare and ghosting.
The Hyper Sonic Motor ensures fast AF, and Sigma claims to have optimised the AF algorithm. The 50mm has a minimum focusing distance of 40cm.
The Sigma 18-200mm f/3.5-6.3 DC Macro OS HSM is a revision of a lens released in 2011. Designed for APS-C format SLRs, the 18-200mm has been reduced in diameter by 4.6mm and forms part of Sigma's "Contemporary" range.
Designed to be useful for close-up work, the 18-200mm has a minimum focal distance of 39cm and Optical Image Stabilisation (though the latter function is not incorporated in the Sony and Pentax versions).
Both the 50mm and the 18-200mm are compatible with Sigma's USB dock (for updating firmware) and Sigma's mount conversion service.
The 50mm will be available for Canon, Nikon, Sigma and Sony mounts, the 18-200mm for Canon, Nikon, Pentax, Sigma and Sony. Pricing and availability are yet to be announced.