The Canon EF 400mm f/4 DO IS II USM lens is a rather unique lens that takes advantage of Canon's diffractive optics technology to help create a lighter and shorter design, perfect for people like wildlife photographers who have to lug around large lenses. This excellent video review takes a look at the lens and the kind of performance you can expect.
Coming to you from Christopher Frost Photography, this great video review takes a look at the Canon EF 400mm f/4 DO IS II USM lens. The 400mm f/4 DO is a pretty unique lens; it sits between the 400mm f/2.8 and f/5.6 both in terms of maximum aperture and price, but it also uses Canon's diffractive optics technology, a neat design that uses sawtooth elements that allow the length of the optical path to be reduced and also reduce the overall weight of the lens, both huge advantages when we are talking about typically massive supertelephoto lenses. This is a real boon for people like wildlife photographers who must carry large and heavy lenses around for long distances and periods of time, especially considering f/4 is a very workable maximum aperture for a 400mm lens. Check out the video above for the full review from Frost.
I wonder if Canon has any plans on making RF versions of its superteles.
I think they will, but it does not seem to be their top priority.
Nikon's version is called phase fresnel.
It has a 300 and 500mm.