Lumix S PRO 70-200mm f/4 O.I.S. from Panasonic is an L-mount telephoto zoom featuring an f/4 constant maximum aperture. A sophisticated optical design is employed, which 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 focus system, which utilizes both a linear motor and a stepping motor, to provide especially fast and precise focusing performance. Additionally, an Optical Image Stabilizer reduces the effects of camera shake for sharper handheld shooting and the lens sports a weather-sealed design for use in harsh conditions.