Som Berthiot zoom 40-70/1.6

the lens alone

There're few zoom projector lenses out there. Faster one is more pricy. I only know the fast zoom projector lens made by good maker. So it must be good one, I think. I bugh another brand years ago, but never made it to my home. lost in nowhere.

the lens set-up with helicoid adapter,

I put it in Olympus E-PM1, as it only cover M4/3 sensor. too bad this set-up only get approx. 2 meters in farthest focus. 

The rear body hit the rear part of helicoid. diameter of the lens is bigger than 42mm.

I need to make it's own helical system to reach infinity