Hi Pieter,
Perhaps the Canon EF 11-24mm f/4.0L USM could be a nice lens for you ¿?
Look at the images below specially the second one which is a 100% crop of the upper left corner and the 3rd image is a 100% crop of the lower right corner
Image shot @11mm f/8.0 iso100 and 1/80s with a 5D mark III