The Sigma 50-150mm f/2.8 EX DC HSM lens is a compact, lightweight, large aperture telephoto zoom lens designed exclusively for digital SLR cameras and incorporats the very latest optical technology. The incorporation of the very latest optical technology gives optimum lens performance providing excellent correction for flare, ghosting and all types of aberrations. High image quality is assured throughout the entire zoom range. When used with a Nikon digital SLR camera, this lens provides an equivalent range of approx. 75-225mm (see note).
DC lenses are exclusively designed for digital SLR cameras. The image circle (rear of lens) is made to match the smaller dimensions used for the image sensor on digital cameras. As a result these lenses are also more compact and lightweight, and are better matched to digital SLR cameras.
Note: HSM lenses, while able to manually focus with all Nikon F-mount cameras, will autofocus ONLY with the following cameras- D1 & D2-series, D50, D70, D100, Pronea 6i, and Pronea S (or newer camera models). With other models, HSM or AF-S lenses must be focused manually. This is the same limitation as Nikon's own AF-S lenses.