Sigma 50mm F1.4 ART DG HSM Lens for Nikon 50mm focal length, Lens not zoomable 75mm equivalent focal length on APS-C cameras, 80mm equivalent focal length on Canon APS-C cameras F1.4 maximum aperture; F16 minimum Ring-type ultrasonic-type AF motor with full-time manual focusing 77mm filters. 77mm filters. 0.4m/15.7" minimum focus. Please use a USB dock for calibrating the focus