Panasonic's Lumix G X Vario 12-35mm f/2.8 Asph. Lens for Micro 4/3 (Black) is a constant-aperture standard zoom compatible with micro four-thirds mirrorless cameras.
With an equivalent (in 35mm format) 24-70mm zoom range, this is a close match for a type of zoom lens that's very popular with photographers using full-frame cameras--from a true wide-angle to a short telephoto focal length and a bright f/2.8 maximum aperture through the entire range.
This lens features POWER O.I.S. image stabilization, nearly silent operation when shooting video, and specially treated glass that dramatically reduces ghosting and flare (Nano Surface Coating), minimizes chromatic aberration (Ultra Extra-Low Dispersion glass), and improves descriptive performance from corner to corner (Ultra High Refractive glass).