Supertelephoto lenses are a love/hate relationship for a lot of photographers: they showcase some of the best optical engineering companies have to offer, but carrying them around is quite a workout. Canon is seeking to cut that weight with its supertelephoto lenses in development.
"Diffractive Optics" is the term Canon uses for Fresnel lenses, lenses that are often formed from concentric layers of glass, resulting in a sawtooth cross-section as opposed to the traditional smooth edge. See the diagram below, which showcases the cross-section of a Fresnel lens vs. a traditional design:
The beauty of the design is the same optical element can be made with much less glass, and in lenses where there's a lot of glass, that can translate the considerable weight savings. They also typically show better control of chromatic aberrations. Canon has demonstrated this with the 400mm f/4 DO IS II, which is lauded for its light weight and substantial optical improvement over its predecessor that consequently brought it into the true professional realm. The technology can also be seen in the 70-300mm f/4.5-5.6 DO IS lens. Now, the good people over at Canon Rumors are reporting that multiple DO lenses are being developed, with a release date in 2018. A 600mm f/4 DO IS was first seen in September 2015 at Canon EXPO, and it was an impressively small lens given the focal length and aperture. Such lenses would be a huge boon for those who have to lug these monsters around on the regular, namely sports and wildlife shooters. Head over to Canon Rumors for more.
[via Canon Rumors]