Sigma has two new lenses that should appeal to owners of the Nikon D40 and D40x. The Sigma 17-70mm f/2.8 – 4.5 DC Macro HSM and the Sigma 18-50mm F/2.8 EX DC Macro HSM lenses are equipped with Hyper Sonic Motors (that’s the HSM there) to enable autofocus with the D40 and D40x.
The new large aperture lenses are also capable of autofocusing with all the other Nikon DSLR cameras. Both lenses have a minimum focusing distance of 20cm (7.9â€).
The Sigma 17-70mm F2.8-4.5 DC Macro HSM for Nikon is built with 15 lens elements in 12 groups. A Special Low Dispersion (SLD) lens and Aspherical lens allows a compact construction and high optical performance. It has a maximum magnification of 1:2.3 for close-up photography.
The Sigma 18-50mm F2.8 EX DC MacroHSM for Nikon meanwhile has a maximum magnification of 1:3. It consists of 15 elements in 13 groups featuring aspherical, SLD and ELD (Extraordinary Low Dispersion) lenses to provide high picture quality throughout the entire zoom range.
[Site: Sigma USA]