This is good to know, regarding the 17-40. Thank you all.
A friend announced to me yesterday, that he just bought the 16-28 Tokina, for his 7D. I hope to try it on my new 6D. Hopefully I will make the right choice. I have a feeling the right choice is to buy several lenses including a T/S, but I would rather not spend the money.
I wonder...does anyone ever try to correct rectilinear distortion? I guess I should google it. That distortion, is why people don't like shooting really wide angle. It's either that, or barrel distortion of a fish-eye...in some cases neither is preferable...which is where panoramas come in. But who has time to do stitched panoramas while visiting a national park or something? I would just wind up rushing it, and miss out on going to enough locations to take pictures. I'm always rushed...time is never on my side. Sort of like posting on here. I sign in to look around for 15 minutes, and an hour later I'm done.