My first post here, so please be gentle
I have the 16-35 2.8L II on test from Canon at the moment and have been comparing it to my 17-40 f4 L
From my field tests I pretty much concluded that the 17-40 was the better lens and that any advantage that the 2.8 "may" offer, was not work the extra coin.
Then I discovered something really weird with the 16-35 and I am starting to think that it's a dud and that I need to test another.
This image is a crop from a 16mm @ f4 sample. It looks like camera movement, but this is 1/1000 sec, tripod mounted, mirror locked up and timer delayed.
and just to prove that there is no movement, here is a section from the middle of the same image...
More samples can be seen here ADPOTD Forum