From the reviews i have seen i noticed that some people have really bad EF 17-40mm copies.
I think it was a guy named RLphoto from here who had a 17-40mm copy that showed corners so bad i first thought he uses a vignete blur.
No honest i have never seen such bad corners with any of my Canon glass.
I own a 16-35mm f2.8 and my brother has a 17-40mm f4.
The 17-40mm from my bother is much sharper in the corner than what i have seen from RLphoto.
So i thank you for this review. It seems your 17-40mm is closer to my brothers in terms of image quality.
The 16-35mm f4 seem to be a nice upgarde but not such a big step in terms of image quality.
Sure nice for pixel peeper but i guess you will hardly see a difference in prints.
Yes, I've heard this as well. My copy is pretty old, from 2007, and it's resolved tack sharp ever since, even with moisture entering into the lens enclosure.
I wish there was a way to determine which eras or batches are good and bad...