Mamiya 645 lenses were already some of the fastest medium format lenses made at f2.8. Adding to the kippon baveyes Speed Booster 0,7x tales these special lenses to a new level, turning most of the lenses into a T2.3 and the 57mm (80mm f1.9 before the rehouse) into an impressive T1.6 . The ability to utilize the full medium format image circle, get an extra stop of light, and avoid the  stills lens housing has breathed new life  into this set.

The Mamiya 645 have a beautiful flare good sharpness and a  added t stop due to the speed booster which also adds  more character towards the edges and a slightly different curvation.