Sigma has announced the 18-35mm F1.8 DC HSM Art lens for APS-C DSLRs – the world’s first constant F1.8 zoom. The lens covers a 27-52.5mm equivalent range, though the company has not yet announced which mounts it will be offered in. There is also no announcement of a recommended price. The lens will offer the light-gathering and depth-of-field equivalent of a constant F2.7 on full-frame, which may under-cut the need for some photographers to change formats.
News: Digital Photography Review (dpreview.com)