DXO rates Canon lenses. Maybe they don't rate ALL Canon lenses,fut they recently added the old (1993 design, still in production) 400mm f/5.6 L. The Canon bodies can't keep up with the Nikon D800 and the new Sony FF mirrorless numbers, merely due to markedly different pixel count. Relative ranking of third party lenses is similar between Canon and Nikon mounts. Scoring of lenses is in part a measure of sharpness and contrast, in part a ranking of aperture. It is hard to compare lenses using the score, because the aperture and the test chart data are not separated. Fine if you want to compare 50mm f/1.4 lenses, not so helpful for specialty lenses. My 400mm f/5.6 L "toy lens" is really quite sharp but scores low due to the f/5.6. Well, I am not hand-holding a DXO score to shoot a bird in flight, I am holding a 3# lens. .