Mirrorless camera systems can't match the versatility of a full-size DSLR. Panasonic's new Lumix G X Vario 12-35mm optic is packing a constant aperture lens, offering consistent large aperture size throughout the zoom range. A constant f/2.8 aperture.
Tthis 12-35mm lens covers the same zoom range of 24-70mm glass on a full-frame camera, in a significantly smaller package. It consists of 14 elements in nine groups including UED and UHR lenses to increase image quality and minimize distortion and has a built in image stabilization and Panasonic's Nano Surface Coating to reduce ghosting and lens flare.
Panasonic has yet to release pricing, but the European price tag has been estimated at €1,100 (about $1,400) -- by comparison, Canon's equivalent optic (from a specification perspective) will run you $1,600.