I have been using my Pentacon Six for some time now with several different lenses and without any focusing issues, but I recently decided to 'upgrade' my Biometar 80. I previously had one of the earliest version without an automatic diaphragm and with it being rather tedious to use, I decided to get a newer Biometar 80. I found one from the newest series (serial number 44xxx) on eBay, did some test shots with an adapter on my Nikon DSLR, found everything to be ok and went on holiday with the Pentacon and the new Biometar. After getting home and developing the films, I realized that all of the pictures were slightly out of focus and shooting a focus test chart with the new Biometar on the Pentacon confirms this. After having focused on the 0 point, the actual focus is distinctly in front of where it should have been. I hadn't had any issues with my other lenses, but to be sure, I did some further tests. Here with the old Biometar 80: And here with my Sonnar 180 (ignore the blur, but I had some issues with my tripod): I also have a Görlitz Meyer Orestegor 500/f5.6 lens, with which I took some pictures during my holidays without any focusing issues. I have however not done any test shots of the focusing chart with that lens. Since everything works as expected with my previously owned lenses, my first assumption was that something is wrong with the new Biometar, but after all, I had done some extensive tests with it on my Nikon DSLR before starting to use it on the Pentacon and had not experienced any issues. To be sure, I mounted the new Biometar on the Nikon again and did some test shots of the focus chart. This combination worked perfectly as well, when mounted on the Nikon, the new Biometar focuses just where it should focus: At the moment, I had the following findings: - the new Biometar has a focusing issue when mounted on the Pentacon - when using any of my older lenses on the Pentacon, I do not have a focusing issue - when using the new Biometar on a Nikon DSLR with adapter, I also do not have a focusing issue I did several test shots of the focusing chart with different apertures and the problem is clearly not any kind of aperture dependent focus shift. The focus point stays the same, even if I stop down the lens. The problem seemed to be related to the exact combination of the new Biometar and the Pentacon. I then managed to get a second new Biometar (serial 45xxx) on eBay of the same version/series, did new test shots of the focus chart and had exactly the same front focus issue with the newest lens as well. So, the most precise definition I can give of my probem is: If I mount a CZJ Biometar 80 of the newest version on my Pentacon Six, the actual focus point is in front of whatever I tried to focus on. If I use the problematic lenses on another camera, or if I use other lenses on the Pentacon, I have no issues and focusing works as expected. Is there anybody out there with a suggestion what might be wrong, or what I might be doing wrong?