Canon EF 75-300mm F4-5.6 III USM Autofocus Telephoto Zoom Lens-Canon 75-300 F/4-5.6 Mark 3 USM Lenses Review. The newly developed Micro USM makes autofocusing quicker and quieter. The improved zoom mechanism also makes zooming smoother. The front part of the zoom ring now sports a silver ring for a luxury touch. www.microglobe.co.uk