When is a Fisheye Not a Fisheye?

Do you hate the fisheye look, or maybe just moderately dislike it? I do... and the more exaggerated the look the more it isn't for me. But, there is a lens that I recently discovered that creates a 180 degree horizontal field of view with only moderate rectilinear distortion. After using appropriate image process technique, it can produce images that are even good enough for some architectural use.
This lens is a 12mm f/2.8 full-frame fisheye lens of stereographic design, made by Samyang, and sold under that name as well as under the Rikonon name. These lenses are identical and from the same factory. Only the branding differs.
The one I purchased is the Rokinon 12mm f/2.8 ED AS IF NCS UMC Fisheye Lens for Sony E-Mount. It is available in Sony E, Canon EF and Nikon F mounts. It is manual focus, and in Sony and Canon mounts has no electronic connection to the camera. In Nikon mount aperture information is transmitted and can be controlled by the came...