I'll be moving to full frame within a few months and I'll be looking at adding an UWA lens to my kit. What I can't seem to figure out is the benefit of version II of this lens versus the old 16-35 f/2.8. Resolution chart comparisons seem to suggest that they each perform better at different focal lengths, both lenses are weather sealed, both have roughly the same design...
Also, version II has 82mm filter threads, an awkward size for sharing.
... Was there a particular reason for updating this lens? The only reason I'm currently considering version II over I is the mark I still sells for about 70% of the price of a new mark II, and I'm generally suspicious of people selling lenses on eBay.
The Mark II is a better lens. The AF on it is smoother than it was on the Mark I (less "jitter", although they are about the same speed), and the zoom ring is smoother as well. Optically, the two are similar, with the Mk I very slightly edging out the Mk II at the long end, however the Mk II definitely does better at the wide end in the corners. When I set out to purchase a wide-angle landscape lens, I evaluated the 16-35 I & II as well as the 17-40. The 16-35 II had the best corners, and when it comes to enlarged landscape photos, having good corners can be a REAL plus.
None of those were really the reason I purchased the lens though...the things that finally sold me were the multicoatings, flare control
, color and contrast. The 16-35 II is a considerable improvement over its predecessor in this area...particularly flare control. FAR less flare, and when it does occur, it often blends so well into the scene that you can hardly see it, and barely affects contrast at all. Generally speaking the color quality and contrast of a lens is not terribly important when shooting RAW (you can do whatever you want with those factors in post), but its nice to know that you can get better results with this lens when shooting JPEG. If you are a JPEG shooter, then the color and contrast of this lens will be another nice bonus over the Mark I.
When evaluating lenses, even between Canon and other brands, one thing that Canon seems to do particularly well these days
is control flare. Compare some other brands considered to be the best optics in the world...such as Zeiss. There are several comparable EF-mount Zeiss counterparts to many of the top Canon L-series lenses. In pretty much every case, Canon newest
lenses will have better...often FAR, FAR better...flare control than the Zeiss counterpart. While the same cannot be said about all Canon lenses, particularly older lenses, their brand new designs or Mark II's for their L-series lenses (stuff released within the last few years), from ultra-wide to super telephoto, have some of the best flare control in the world. This can be seen in the EF 8-15mm f/4 L Fisheye, EF 16-35mm f/2.8 L II, TS-E 24mm f/3.5 L II, EF 24mm f/1.4 L II, 70-200mm f/2.8 L II, etc. If you are buying a lens for use in any situation where the sun or any artificial light sources may cause flare, the newer and more expensive version of a Canon lens will
offer something of value above and beyond the older, less expensive version.