Originally posted by Parallax After eliminating the Sigma it comes down to the 20-40 vs 16-85.
The 20-40 gives me no capability beyond convenience that I don't have. at 20 it's only 1/3 stop faster than my 21 Ltd and at 40 it's a full stop slower than my 40 Ltd, and in the mid range about 2 stops slower than my 31.
OTH
The 16-85 gives some advantage over my Sigma 18-250. It's wider by more than 10%, it's lighter, it's WR. Besides that, though I'm happy with the sharpness of the 18-250 the 16-85 is apparently about as sharp for a normal zoom as you can expect; at least in a price range mere mortals can afford.
Hm. I think I just talked myself into a 16-85.
Very few people have expressed dissatisfaction with that lens bought new. It's much less affected by the differences in personal taste. Although, you still have to get a good copy.
I seriously doubt anyone with a stellar copy of these lenses ever wants to sell them. I'm tempted to ignore second hand copies, if that guy didn't think enough of the lens to keep it, why would I? The exception being older glass, that isn't a big gamble in terms of money spent.
I sometimes wonder how much dissatisfaction with the 18-135 is the same low end copies being passed around. I've had mine since 2011 and you won't ever see it coming up for sale. Although if I were buying today, I'd probably go for the 16-85, especially with the 55-300 PLM being such an excellent lens, if I want to collect the whole set.