Greg here is all of Canons lenses where you can see the MTF diagram for each lens.
http://www.usa.canon.com/cusa/consum...ef_lens_lineup
There is a guide somewhere on the web how to interpret these diagrams.
The dotted lines show the MTF for wide open and f/8 both tangential and saggital and different lines/mm test patterns. I cant remember exactly.
You will see that a short focal length lens with near perfect off axis performance does not exist.
Below is the MTF for a Canon 300mm F2.8L IS. The non IS version is even better than this.
Next is Canon 24mm F1.4L II USM
The MTF is far worse especially off axis.
MTF will vary with focal length what you should compare is the MTF on axis with the MTF anywhere off axis for the same aperture curves ie tangential and saggital for each lens. MTF is modulation transfer function and is a quantitative measure of resolution.
The LHS scale of the diagram is the MTF. 1.0 is perfect. Along the bottom is the distance in mm off axis.
Bert