ThePhoBlographer (Click here) tested the newest of all Micro Four Thirds lenses, the Samyang (Rokinon in USA) 7.5mm fisheye: “I want to recommend this lens to everyone simply on the matter that the build quality is something that everyone should experience and that this lens is truly how Micro Four Thirds manual lenses should be created. The lens exhibits exceptional sharpness, color rendition with no fringing, little to no vignetting, and meters well with the camera. It’s a lens that everyone would ask for.”
You can find plenty of image samples taken with the lens on his website!
And ePhotozine (Click here) tested the much more expensive Panasonic Lumix G 8mm Fisheye Lens: “The compact size, and excellent optical performance of this fisheye optic will make it certainly worthy of consideration if the distorted fisheye effect is what you’re after.“.
You can click these links t check price and availability Amazon, Olympus US store, Adorama, B&H, eBay.