The optical stabilization helps to reduce camera shake induced blur and allows you to use slower shutter speeds than would otherwise be possible. The hypersonic focusing motor makes for quicker autofocusing.
The Sigma 50-200mm f/4-5.6 DC OS HSM will be available for Sigma, Canon, Nikon, Sony and Pentax DSLRs.
More details from Sigma’s press release below. [Read more...]