http://www.lensrentals.com/blog/2014/12 ... comparisonCanon shooters have a bit of 400mm excitement right now. The biggest news, of course, is the release of the 100-400mm f/4.5-5.6 IS II lens, replacing the original version that's had a very long, successful run. Not quite so much excitement was generated by the release of the 400mm f/4 DO IS II lens. It too replaces a long running lens, but one that has been considered more of a niche lens. (I'll admit, though, it's been one of my favorite niches. I used the 400 DO a lot over the years.)
Opmerlijke verbetering van de 400mm f/4 DO IS II
But when just comparing these two lenses, the difference in resolution between the original 400mm DO and the Mk II version was rather amazing to me. Canon said the new version has, "gapless dual-layered diffractive optical (DO) elements that help improve optical performance". Well, it certainly does.