The Lumix S PRO 16-35mm f/4 from Panasonic is an L-mount wide zoom featuring an f/4 constant maximum aperture. An optimized optical design incorporates a series of aspherical, low dispersion, and high refractive index elements, to control a variety of aberrations, color fringing, and distortion for sharp, clear, well-corrected imagery throughout the zoom range. Complementing the optics is a unique double-magnet linear motor focus system, which provides high-speed response and power while remaining compact in size. 

Wide-angle zoom is designed for full-frame L-mount mirrorless cameras, however, can also be used with APS-C models where it provides a 24-52.5mm equivalent focal length range. Three aspherical elements and one ultra-high refractive index element help to minimize distortions and spherical aberrations throughout the zoom range in order to maintain edge-to-edge sharpness and illumination. The autofocus focus system employs a double-magnet linear motor to deliver impressively fast and precise focusing performance while remaining compact. A focus clutch mechanism has also been incorporated, which allows for near-instant AF/MF switching.

Panasonic Lumix S PRO 16-35mm F4 Specs..