For those with long memories, the introduction of the Canon 400mm f/4 DO in 2000 occasioned a lot of excitement. It was the first camera lens to use diffractive optical elements, and seemed to presage a future in which the super-telephotos would be significantly lighter and more compact (if not, alas, any less expensive). Early reviews were very positive. Fast forward 14 years and super-telephotos have indeed gotten significantly lighter, due to the use of new materials, but of diffractive optics we’ve heard scarcely a peep. Canon did introduce a 70-300mm f/4.5-5.6 DO – which sits uneasily in the lineup as neither the lightest nor sharpest 70-300 – but the expected expansion of green rings elsewhere in the high-end hasn’t happened.
Perhaps we should add, yet. If the 400mm f/4.0 DO I rented for the Tetons (from the always excellent LensRentals) seemed like a bit of a lens design dead-end when I placed the order, by the time it arrived at FedEx it was a dinosaur, courtesy of Canon announcing a version 2 of the lens. Unless you already own one, it’s unlikely that you or I will ever shoot with the original again. Diffractive optics is the future, once more.
How did it perform? In one word, outstandingly! The normal complaints one hears about the 400mm DO are that (1) it’s not as contrasty as the other super-telephotos, (2) it flares more easily, and (3) the bokeh is odd. These may well be valid gripes (and indeed Canon implicitly acknowledged the flare issue in their blurb explaining why the version 2 is better), but in practical use I didn’t find them a problem. And the benefit of the lighter weight is undeniable – this is a pretty fast stabilized super-telephoto that can realistically be hand-held for extended periods of time. I enjoyed using it for both landscape and wildlife shots.
I’m always slightly amused to read internet commentary that seems to implicitly assume that when you buy one of Canon or Nikon’s most expensive lenses, you have the right to expect it’s the best lens they know how to make. Self-evidently it ain’t so. Better lenses could certainly be designed, but actually realizing them in glass and metal would require some combination of heavier optics, more exotic materials, and better manufacturing tolerances, all of which would mean higher prices. Zeiss’ marketing for the Otus line notwithstanding, even the “best” lenses are compromises between cost, weight, maximum aperture and sharpness, and when weight is an important consideration the 400mm DO (and no doubt its successor) may well be the best choice.