"Sigma 50-100mm F1.8 DC HSM Art Building on the groundbreaking Sigma Global Vision 18-35mm F1.8 DC HSM Art Lens, the new Sigma 50-100 F1.8 (75-150mm on 35mm format) mid-range zoom lens embodies the same engineering prowess to deliver outstanding prime lens-like results. Factoring in the APS-C image circle of 1.5x, the 50-100mm F1.8 covers three popular short tele prime focal lengths: 85mm, 105mm and 135mm. Like the 18-35mm F1.8, the new 50-100mm F1.8 maintains a constant F1.8 aperture yielding exceptional brightness and resolution throughout the zoom, while simultaneously maintaining focus as the lens is zoomed, a feature videographers will greatly appreciate. Sigma Art Line Image Technology Innovation Features three FLD (F Low Dispersion) glass elements, one SLD (Special Low Dispersion) glass element, and one high-refractive index, high-dispersion glass element to minimize aberrations. Redesigned and enhanced, the new Hyper Sonic Motor is 30% slimmer and provides fast and accurate AF. Highly durable polycarbonate diaphragm made with fluorine; blades feature carbon feather film offering exceptionally smooth operation even during continuous shooting. Outstanding Zoom Lens Maneuverability Inner focusing and zoom design offer versatile shooting options Tripod socket for stable, comfortable operation Features 21 elements / 15 groups, Minimum Aperture: F1.6, 82mm filter thread, Minimu"