I've been fiddling around, fixing a Russian Jupiter-12 lens that wasn't focusing correctly, and I realised I had a way of checking ir. The Jupiter-12 is a Russian-made version of the Contax Biogon, a 35mm lens which, alas, won't fit the modern Voigtlander Bessa cameras which take Leica-screw lenses. What I needed was some way of checking infinity focus, There's a trick of using a camera, with a long lens, as a collimator. An object in the film place will, with the camera lens set to infinity, appear to be at infinity when looked at through the camera lens. So if you look through that camera lens with an SLR, its lens set to infinity, a sharp image proves both lenses are set correctly. When I'd figured that out, it was quick to set up. A broken CD case gave me a fiece of clear plastic I could use as the object, with a few lines scored on the plastic. Open the back on the old Fed-2, set the shutter to B, and use a cable release. And you can see the image go out of focus as you turn the focus ring on the lens. What was wrong? The lens assembly is screwed into a carrier, which the focusing mechanism moves. It had worked loose. (And it was worth cleaning the old, dried, grease off the threads.) Now just to get some photos as a final check...