Medium telephoto lens fast f2 aperture usm focus motor with full time manual focus 90cm closest focusing distance 58mm filter size super spectra coatings reduce ghosting and flare the ef 100mm f2 usm is a short telephoto lens with a wide aperture making it ideal for portraits the lens compresses facial features and ensures the subject stands out against a blurred backdrop long focal length and compact size the ef 100mm f2 usm has a large maximum aperture but is still relatively compact the 100mm