Panasonic Lumix G 8mm f/3.5 Fisheye Aperture Series (Wyman Cabin Exterior)
Really good! A must-have lens for the serious Micro Four Thirds shooter. It is also my most favored lens for cycling videos.
At about $610, it is priced fairly for the high performance it delivers. Olympus makes a $799 8mm f/3.5 fisheye, but it’s a Full Four Thirds lens, and so would have to use an adapter to work on the E-M5— which would substantially increase the overall bulk.