Upload & Sell: On
The DXO boys have done their test chart shooting evaluation of Canon's and Nikon's 600mm f/4 lenses, and here's their report.
I do not have enough patience to read that stuff beyond the synopsis, however, even if all other performance parameters are similar, my opinion is that the 5.06 kg lens (Nikkor) is majorly outclassed by the 3.92 kg lens (Canon) when it comes to ergonomics, and the resulting manner and scope of use. Like night and day.
I looked at it a bit and was puzzled by the bodies they were using to do the comparison - 5diii vs d800.
D800 is 4 fps. I would not think that bird/animal photographers would be using a d800. Even the 5diii at 6fps is a bit weak. They should have compared 1Dx (12fps/18mpx) vs D4 (10fps/17mpx).
Then they conclude that Nikon matches Canon because, even though 600 f4 v2 canon is better than Nikon equivalent, the D800 resolution causes them to be even.
In virtually every category, the Canon does significantly better (lower distortion, lower CA, less barrel) but they conclude even because of the d800.
I don't agree with their conclusion:
1) Canon is lighter
2) Canon has better iq when you have equivelent bodies
3) The bodies they compare would not likely be used (particularly d800) for wildlife/birds
4) People buying 600 are buying it for 5 years not this year alone and Canon is likely to produce a high mpx camera that could match the resolution of d800 but likely no one would want it for this purpose.
5) In addition, I don't like Dxo sharpness measure - it is obscure. I often find if I look at thedigitalpicture side by sides that even if two lens are ranked similarly I would prefer one over another because sometimes Dxo ingnores the edges and ranks the highest IQ at optimal fstop rather than the lowest fstop etc. In other words, I cannot tell what they are measuring with their sharpness scale and are they comparing f5.6 vs F4.
6) Nikon is cheaper
And from the data - I would say, ignoring cost, and using a wildlife orientated body the Canon 600v2 is a significantly better lens for iq and ease of use - and is a clear winner.
Nikon does have some better lens than Canon but not many. The d800/14-24 is my only temptation to have two systems. And now that canon 200-400 is better than the nikon 200-400 (1.4 built in alone makes it better), I am less tempted to Nikon. But if Canon does not match the mpx and dynamic range soon, I might be tempted to d800/14-24.