Sigma's 17-70 mm F2.8-4 DC macro OS HSM is the practical zoom! A large-aperture, standard zoom lens for digital cameras with an open-aperture value of F2.8 (at 17 mm) & covers the most frequently used focal lengths. With an aperture fast enough to be used in many light situations, its close focusing for use with very small object & its outstanding optical performance make this an ideal all-around lens for landscapes, portraits, still life studies, group shots & just about any everyday photo situation. The OS, Sigma's anti shake feature, offers the use of shutter speeds Approx. 4 stops slower than would otherwise be possible. HSM ensures quiet & high speed AF capability. With a faster aperture than the typical camera "kit lens" it is an excellent choice for the photographer who has higher expectations for their photo equipment.