16-35/4.0L IS not much better than the 17-40/4.0L

Okay, I am probably one of the first people who says something a little negative about the new 16-35.

I do have both of those lenses now and I was expecting the 16-35 to be much better in every way.
I tested them side by side and I am a little disappointed now. Yes the 16-35 is better in some ways. But not in every way.

17-40L pro's
- Sharper center
- Less vignetting

16-35L pro's
- A little sharper in the corners (seriously, not that much)
- Less chromatic aberration

And I tested the IS vs non IS and I could not see a dramatic difference in keepers.

I tested the lenses outside and inside and got quite a few miss-focussed shots from the 16-35. When I came back home I MA the lens to +6 on the wide end, so I hope it will be a little better.
It was really cloudy today, so I hope I can see more differences in better weather, but for now, I am not really convinced yet.

I don't know if I would have bought this lens if I knew that the differences are not that big.
I really hope that my opinion will change in the future when I use this lens more. But I will give you one advice. Test a 16-35 before you upgrade your 17-40L! Maybe your thoughts would be the same as mine.

Care to share any samples?

Perhaps you had too high of expectations? I haven't used either yet (although the 16-35mm is very tempting) but reviewing slrgear it appears that yes the corners are a bit sharper depending on the centering quality of each lens (their 17-40 was a bit decentered). In addition the CA is significantly less pretty much universally.

The sharpness and CA at the tele end of the lens is significantly better.

As for IS not helping...what shutter speeds were you shooting at. On my 35 IS I was able to test at 1/6th a second a turn IS on and off...the difference was fairly clear.

Post your comparison shots and 100% crops to show those similarities. Then we will know what you are talking about.

The last measure of performance, in any field of endeavor, is always disproportionately expensive. That little bit is worth a lot of money to some folks. To others, not so much. I am squarely in the 'not so much' category. For me, good enough, usually is.