slclick said:
16-35 f/4 for certain. Better copy to copy variation, sharper corners, sharper centers, wider, newer coatings etc. This is an easy choice.
+1...yep the 16-35 f/4is tends to have better everything. Note the superior copy to copy variation.
OP, you do say that walk-around is one of the functions for your new lens. This presumes no tripod. As a full time photographer who has used the dreadful old 17-35L (introduced 1996) followed by 8 years with the 17-40 f/4, followed by a few disappointing years with the 16-35 f/2.8II. A couple of months ago I picked up the new 16-35 f/4is. What slclick says is true. It's a highly dependable lens. Read the reviews. They're overwhelmingly positive.
The 17-40 f/4 (introduced 13 years ago in 2003) remains good value in some respects, but is really showing its age now. There may be rare copies around that are actually sharp wide open but most deliver pure mush at f/4. One click down to f/5.6 and it's very capable right through to f/11. I tended to think of mine as a 17-40 f/5.6.
The clincher for me came from a colleague who shoots a lot of difficult aerial projects. The client needed dusk aerials of their casino with the giant gas flares lit up, but showing the adjacent river and the city skyline as well. So by implication it was a wide shot. Shooting out of even a very smooth helicopter at dusk is going to be a huge challenge. As a form of insurance he shot with three bodies. One with 24-70 f/2.8II, one with 16-35 f/2.8II and a third body with a loaned 16-35 f/4is. And guess what? Even giving away a stop in brightness, the 16-35 f/4is convincingly saved the day (and a
lot of money).
Get the picture from this and other posts? The 16-35 f/4is is a class act. For the first time in twenty years I have a UWA zoom that I can trust wide open for projects from very discriminating clients. If you can't afford it, save for it.
-pw