Thanks for your reply. I was wondering if the shorter cone and 135mm focal length would work on the 150mm lens track. I don't recall what specific type of lens the track is for. Much of the information is difficult to read. I think I will take your advice and just get a good 150mm enlarging lens. Probably an easier fix than trying to track down the proper lens mount cone size. I have already spent several hours and uttered many foul words dealing with this specific issue!