My foray back into panoramic photography gave me an excuse to buy a DSLR. Owning a DSLR has given me an excuse to search eBay for deals on interesting camera lenses. In December that led to the purchase of a Nikon 600mm f/4 AiS manual focus super-telephoto lens. My particular copy appears to have been owned by the Dallas Morning News at some point—as that's written on the side of its trunk case. I trust it is a good retirement activity for this lens to look at birds and airplanes; activities which I also enjoy. It's incredibly heavy and impractical to carry around, but along with my modified TC-20E III, it's pretty much like looking through a telescope. I also added a dandelion CPU to the lens to get some of the benefits of more modern kit, like focus priority shutter and EXIF lens info.

That excellent eBay deal unfortunately meant there were a few compromises, like the beat up case. The most significant was that the lens was missing the HE-5 Hood Extension. Having such a large front element meant that it's tricky to shade the front element from incident sun exposure, which can cause washed out images and lens flare. It took about 6 months to find a hood on eBay, so I bought the first one I ran across, even bidding it up while on vacation.

I was elated to finally complete my kit by adding this part—but it turned out upon receipt, the hood extension wouldn't mount to the end of my lens. After a bit more research online, I was able to determine there were 2 plastic mounting tabs missing from the hood. These were subtle and frankly I hadn't noticed them on any pictures of hoods while researching and purchasing the hood online. The seller was happy to help get things straightened out, but had no ability to magically conjure up these parts. I decided that instead this would be an opportunity to restore a rare old piece of equipment and keep it from the scrap heap. The missing knob was easy (albeit expensive) to come by from Nikon, as the part is still used on modern lenses. The screw on the new ones is a bit longer, so I just removed the black aluminum cap and screwed it into place. Next were those pesky tabs. I knew it'd be impossible to find original tabs I needed, so I studied all the photos I could find, approximated what size they'd need to be to mount the lens, and started modeling in Fusion 360. I asked for some help on the DPReview forums, and got some help from the community there. A quick trip to the Shapeways website, and I had my first revision in hand.

Of course the first revision didn't fit, so I sanded them down, made them work, and modeled up the second revision. This time shrinking the tabs and rounding them off for easier mounting. The trimmed down version worked like a charm, and Shapeways was very kind in replacing one of the two that came out a bit deformed from the printer. Their new Professional Plastic (HP PA12 Nylon Plastic) is extremely durable and seems like it'll be perfect for this kind of mechanical part.

The final trick was locating original screws to match the 25-year-old ones in the hood. This one was trickier than expected. While it was soon clear the screw diameter was M2 and length was 5 or 6mm, I couldn't quite make sense of the 0.6mm thread pitch and kept questioning my caliper measurements. I spent about a week searching through different screw standard specifications until I finally encountered the JCIS Type-B Thread Forming screw. It turns out this screw is specially designed to be self tapping, and the body of the screw is in fact more like a rounded-off triangle than a cylinder—a design I eventually learned was called "trilobular." Of course it had a standard JIS cross point (not philips) drive and was black in color. Knowing the screw specs was helpful but not sufficient because however hard I tried, I couldn't find a supplier in the US. Eventually Saima Corporation in Japan responded favorably to an inquiry for a quote, and I soon had 1000 of exactly the screw I needed. (Please let me know if you need any of the 996 remaining screws I now own…) They were an excellent help to completing this project.

I still have a bit of restoration to do on the 600mm f/4 AiS. I need to craft a workable lens cap and the rubber ring on the end of the lens is still missing (anybody know of reputable 3d-gasket printing outfit?), but these all seem doable now that I've got a working hood extension!

I'm looking forward to more birding expeditions this fall, no matter the angle of the sun. :)

HE-5 Tab
3D Model