You don’t hear a lot of those Kowa MFT lenses you can find on Amazon US, Amazon DE, Amazon UK. But they seem to deliver a nice IQ. ePhotozine posted the full Kowa Prominar 8.5mm f/2.8 Micro Four Thirds Review:
The Kowa Prominar 8.5mm f/2.8 is a classy looking lens, it’s beautifully made and the results are excellent. AF would make focusing much easier, but it can be worked around and still leave the lens being very satisfying to use. At least with the large amount of depth of field available there is some leeway at longer distances.
In summary, it’s a great lens that is delightful in use and delivers the goods.
They also tested the Kowa 12mm f/1.8:
The Kowa Prominar 12mm f/1.8 is a classy looking lens. It’s beautifully made and the results are excellent. AF could be a useful addition, but on the other hand we have an easy to focus lens here that presents none of the focusing difficulties of its 8.5mm sibling. It’s expensive perhaps compared to some, but looks excellent value against the Voigtlander 10.5mm f/0.95, unless that extra bit of speed is needed.
It’s a very compelling lens to use, very much the traditional 24mm (in full frame terms) with all its inherent versatility.