I have found the FE1635 to be the best ultra wide-angle lens for capturing landscapes and architecture.
It is performing at its best at the short focal lengths (16mm) and is the perfect match for even the A7R.
Check out my Flickr gallery (I have included full resolution files, images captured wide open and posted links to Raw files)
https://www.flickr.com/photos/markgaler/sets/72157647309662617/with/15058237158/