Sony Vario Sonnar T* 16-35mm f/2.8 ZA

Manufacturer's Description:

"It is constructed of 17 lens elements in 13 groups, including an extra-low dispersion (ED) for exceptional clarity and center-to-edge resolution and a super ED glass element for much stronger correction of chromatic aberration or discoloration. It also features three aspherical lens elements that provide greater brightness from center to the edge of the image field."