I expect this effect varies from copy to copy. I have had a tough time falling in love with
any of Canon's wide angle zooms. Shooting a brick wall at 10 meters, I think you would see this field curvature; however, subtle changes in the focus might mask it. I have seen
this effect on this lens mentioned before.
Dropped the lens off at Canon Service. The tech acknowledged something was wrong with the lens after seeing some sample pics. He wasn't too sure he can fix it, but he is going to try nonetheless. Keep you posted.
When I first saw your photo of the woman on the patio, I didn't see a problem. But your later "undulating wall" showed convincingly a "bubble" or ring in the focus plane. Weird. Glad you pursued the matter.
