Many years ago I bought a used lens online, a Micro-Nikkor 55mm f/2.8 AI-S. When I finally got around to trying it out, I realized that the aperture diaphram was stuck wide open. By then the guy who sold it to me was long gone, so no redress.
This was a common problem with this model. Excess oil would get on the seven diaphragm leaves and gum up this delicate mechanism. I investigated and found it would cost as much as the lens is worth to have it repaired. So I resigned myself to owning an expensive paperweight or using it only at its widest aperture, f/2.8.
Today I was going through my case of old lenses and re-discovered my paperweight. Suddenly, it occurred to me that maybe I could fix it myself. Isn’t retirement wonderful? I looked online and found a Japanese site with pictures, but as far as I could tell, the pictures told a story of what not to do (but my Japanese is pretty rusty, so I may have missed the point). Then I found an English site with useful how-to instructions, but no pictures. I scanned the text, decided it was doable even with my fading eyesight, and jumped in.
I am always good at taking things apart. My lens was in a heap of pieces in 10 minutes. Then the fun began. I was to disassemble the diaphragm mechanism, clean it, and re-build it. I studied the instructions and thought, nah – there has to be a short cut where I don’t have to disassemble this. But try as I might, it all fell apart anyway, so I had to go for broke.
The diaphragm mechanism consists of seven tiny blades, each with two much tinier brass hinge pins, so as to provide a double articulation. These leaf blades are installed in overlapping fashion and sandwiched between two circular plates, where one plate has holes for one set of hinge pins, and the other has slots for the other set of hinge pins. Getting this all lined up so the pins fit in the holes and slots of the cover plates seemed initially improbable.
During the operation, the surgeon lost two pieces. A tiny spring flew across the room as I tried to remove it. But I heard it land and got very lucky in finding it. Then I realized I only had six diaphragm blades on my desk and my heart sank. I very gently moved my chair and stood up. There under me was the other blade. Somehow I had managed not to step on it or roll my chair over it. I could breathe again.
Oil was everywhere throughout the assembly. I cleaned each tiny piece with alcohol and a Q-tip, and got the diaphragm assembly back together in just four tries. After the second try, I sensed how much over my head these waters were. But then I re-read the instruction and realized I was working upside down. Rather than inserting the slotted pins first, I needed to insert the hole pins first. Then it became doable and I got it put back together in just two more tries.
Here’s the amazing thing. The diaphragm was now working smoothly. That provided me with one of the strongest ‘damn I’m good’ moments in recent memory. Also, it was fun to see and understand the intricate design of the diaphragm. In a half hour I went from a feeling of hopeless lack of understanding to a feeling of competence and enlightenment. Successful DIY is the best kind of soul food. I am now possessed by the zen of lens maintenance.
Re-assembly consisted of twisting, turning, poking, and prying the lens assembly back into the lens body. It required lining things up and visualizing how the assemblies worked together. Thank you Nikon for making it impossible to put it together in some non-workable way. It finally clicked into place, the mount assembly screwed on without a hitch, and the job was complete.
I took my rehabilitated lens for a spin in the back yard this morning. The following picture, 1/250s, f/11, shows a sharp general purpose lens with good color rendition. The scene also demonstrates the new camera’s enhanced ability to handle a scene with white flowers in the foreground and deep shadows in the background, and to provide detail in both areas.
See the page on close-up photography for examples of macro images made by this lens at 1:2 and 1:1 magnifications.