Always on the lookout for exploitable market niches, both Nikon and Canon have been building out the middle of their lens catalogs with f/4 enthusiast versions of the expensive f/2.8 zooms favored by pro shooters. Lenses such as Nikon’s 16–35mm and 200–400mm f/4, and Canon’s 17–40mm, 24–70mm, and 70–200mm f/4 all share basic traits: They’re more compact, lighter, significantly less pricey, and (obviously) slower than their f/2.8 counterparts.
