I tested the focus by putting some satin scotch tape on the film plane and opening up and camera at bulb and setting it to something at infinity. It looked soft. So i adjusted focus until it looked sharp. I was at around 3m for infinity to be sharp. I took it one step further and cycled through the focus and it looks like the focus at infinity will go out of focus when focussed close, progressively get sharper, hit 3m, then start getting soft again before the lens stops at its mechanical infinity.