I have the Mamiya 645 Kipon focal reducer for the S1H and the 80mm at f1.9 it's a bit soft and the image seems to glow a bit. I think that might possibly be an issue with the speedbooster not being able to handle fast apertures, rather than the lens. I heard someone else who had the same issue with this combination. You can very briefly see this in the video I shot below, at the 1:20 mins mark, when I open up the aperture to max for a second. It's more noticeable in bright conditions than in low