After opening a lot of eyes with its 30mm, F1.4 DC HSM lens, Sigma's just thrown another curve at the photo community with a feat that the major players haven't managed so far: a zoom lens with a fixed, sub f/2.0 aperture. The Sigma 18-35mm f/1.8 DC HSM that launched today for Canon APS-C cameras flew under everybody's radar and flaunts over double the light-gathering powers of the priciest zooms, which typically top out at f/2.8 -- except for Olympus' $2,300 14-35mm f/2.0 Four Thirds model. The extra third of a stop over that model may not seem like much, but the company said it needed to "solve a variety of technical challenges" to build it in order to minimize distortion and aberration. Sigma's also promising fast autofocus via a hypersonic motor (with full-time manual override) and rubber-coated brass construction. There's no pricing or availability yet, but don't expect it to be cheap (think $2k plus) -- after all, it's the only game in town for now.