Talk about tempting fate! Just two days after posting a walkthrough of how easy it is to get an Industar-69 to reach infinity focus without any modifications to the lens body, I received a copy of the lens that didn’t have enough travel in the focus helix for that method to work. But rather than give up on the lens, I thought I would try modifying it to give the lens block enough rearward travel to reach infinity focus, following in the brave footsteps of Hamish Gill and Brian Sweeney. I’m pleased to report that the modification is simple, takes only 5 minutes if you have a Dremel rotary tool and was completely successful. I’m not going to repeat the earlier walkthrough here; I’ll assume you reached the step where you mounted the lens (without the focus ring) on your camera and found that you couldn’t reach infinity focus even with the lens block screwed fully into the base. If that’s the case: • Remove the lens from your camera and the adapter. Remove the lens block from the base. Clean any grease from the threads on the lens block and the base; set the lens block aside. • If you look at the base, you will see a raised lip around the opening for the threads. You are going to completely remove this raised lip by sanding or grinding it down flush with the interior of the base. This should give the lens block enough additional rearward travel to reach infinity focus. Subscribe to see EXIF info for this image (if available) • Remove the focus stop screws from the base. Attach a sanding drum or grinding wheel to your Dremel tool. Work the sanding drum or grinding wheel around the raised lip until it has been completely removed. Subscribe to see EXIF info for this image (if available) Subscribe to see EXIF info for this image (if available) • Smooth the worked surfaces, especially the newly-exposed thread edges, with some 220-grit aluminum oxide sanding paper and fine garnet paper. Be careful that you don’t cut your fingers! The interior of the base does not need to perfectly smooth, but the threads do, especially the starting cuts. • After you have completely removed any swarf and sanding dust from the base (electrical parts cleaner or any paint-safe solvent is helpful here), grease the lens block and screw it into the base as far as it will go. Leave the focus ring off for the moment. Mount the lens on your camera and see if you can reach infinity focus. The extra couple of millimeters of travel you gained by removing the raised lip from the base should have done the trick. If not, the only other thing I can think of is sanding/grinding/milling the face of your adapter to bring the lens a couple of millimeters closer to the sensor. • If you find that you can reach infinity focus but that the focus feels a little rough in spots, remove the lens block from the base, clean all of the grease from the threads on the lens block and the base and run your fingers over the threads to find any rough edges, especially at the starting cuts. Use the fine garnet paper as needed, completely clean the threads, re-grease and re-fit. If you can’t feel any rough edges but still aren’t satisfied that the focus is smooth enough, there may be rough spots in the sides or bottom of the thread cuts. Since you can’t reach those spots with the garnet paper, rub some toothpaste on to the threads, screw the lens block and base together and twist them back and forth until the focus smooths out. Subscribe to see EXIF info for this image (if available) Sounds weird, I know, but toothpaste is a mild abrasive after all and is very easy to clean from the threads when you are through. Plus, it leaves your lens smelling minty fresh! • Follow the rest of the steps from the earlier walkthrough to reassemble your lens and reset the aperture mark. Enjoy your "new" lens! • UPDATE: Although I was very pleased with the performance of the lens after this modification, I was frustrated that I couldn’t also get the infinity focus mark to line up correctly. When the lens was adjusted for infinity focus, the focus ring would stop turning at about the 5m mark. When the focus ring was adjusted to allow the infinity focus mark to line up correctly, the lens wouldn’t reach infinity focus. What I finally realized was that the lens block was screwed so far into the base at infinity focus that the focus ring was bottoming out. A close look at the front of the lens revealed that, when the lens was adjusted for infinity focus, the face of the lens block was pulled slightly below the face of the focus ring. The solution was to sand a millimeter or so off the bottom of the focus ring – which was a simple but slightly tedious process. Because you want the bottom of the focus ring to remain absolutely level and even, and because the focus ring isn’t terribly robust, I don’t advise taking a file or Dremel to it. Instead, lay a piece of 150-grit aluminum oxide sanding paper on a flat work surface and rub the focus ring around in circles on it, turning the ring in your hand frequently to keep the sanding even. You don’t need to remove a lot of material from the bottom of the focus ring – after a couple of minutes of sanding, carefully clean all of the sanding dust from the ring, check your infinity focus, re-install the focus ring and see if the infinity focus mark will line up correctly. If not, continue sanding as necessary. Once you can reach infinity focus with the infinity focus mark correctly lined up, remove the focus ring and smooth the bottom with 220-grit aluminum oxide sanding paper and then with fine garnet paper. Clean, re-install and enjoy.