The tamron 70 300mm f4 56 sp di usd lens offers unparalleled optical performance in a fast and steady telephoto zoom its advanced design features an ld low dispersion and an xld extra low dispersion lens element to help prevent chromatic aberration and provide sharp contrast the 70 300mm f4 56 sp di usd is the first tamron lens to be equipped with a usd ultrasonic silent drive tamrons very own ultrasonic auto focus drive mechanism for faster focusing making it a perfect telephoto zo