Is there anyone who has this lens and uses it on a µ4/3 camera? How does it perform wide open? At what aperture does it become really good? Any good alternatives, maybe the Minolta 50mm f/1.2? I have a Nikkor 50mm f/1.8 which is very good by f/2.8. If I can get a 50mm f/1.2 at the right price, I'd like to get more speed with good quality.