The Nikon Prostar 7x50 has BY FAR the finest (least) edge distortion of any binocular I have ever held in my hands. And not by just a small amount, but by leaps and bounds. In fact, edge distortion seems to be nearly absent.
The best of the best that I've measured Nikon ProStar 7x50 then Fujinon FMT-SX 16x70 Pentax PCF WP 16x60 Nikon SE 12x50 Fujinon FMT-SX 10x70 Fujinon FMT-SX 10x50 Celestron Regal 8x42 Roof Nikon SE 8x32 Oberwerk Mariner 7x50
Hmmm. . . As I look over the models on my shelf, I wonder how the Fujinon FMT-SX 7x50 (porro) and the Pentax DCF ED 10x50 (roof) compare to this list?