Flare is one area where diffractive elements could have a negative effect, but by facing the diffraction gratings against each other, Canon seems ... just -0.3 EV. An 800mm lens is difficult ...

There are so many EF lenses out there that this ... super telephoto zooms top out at 600mm, Canon takes things a step further, offering a mighty 800mm. Its aperture value of f/9 at the long ...