Not long ago, Sigma announced the fastest aperture zoom lens made for a full frame camera: the 24-35mm f2 DG HSM Art. With a constant f2 aperture range throughout its zoom range, it is the fastest constant aperture full frame lens made so far. But with that comes what many believe to be a big tradeoff. The lens has a very limited zoom range and essentially gives you three big focal lengths: 24mm, 28mm and 35mm. However, these lengths are made possible by 18 elements working together in 13 groups in conjunction with a 9 bladed aperture.
And at under $1,000 this lens any many others that Sigma makes may be some of the few things keeping you working with DSLRs.