Quote Originally Posted by Michael R 1974 View Post
OP asked a technical question. I responded with a technical answer. Distortion is a practical difference between most RF and SLR wide angle lenses. Distortion is not typically a problem in landscapes but for those of us who often shoot subjects with straight lines parallel to the the edges of the frame distortion is visible and distracting. It has nothing to do with test charts and graph paper. Sorry.
I totally agree.

There are circumstances, taking pictures of architectural features, where straight lines are important and distortion, if present, can be very evident and quite disturbing.