The 70-200mm f/2.8 lens is the workhorse of choice for photographers in a wide range of genres, but such lenses are both heavy and quite expensive. For those who want the versatility of those focal lengths but don't need that f/2.8 aperture, a 70-200mm f/4 lens is a far cheaper and more portable option. This excellent video review takes a look at Canon's mirrorless version of the lens, the RF 70-200mm f/4L IS USM.