This is a beautiful example of the old Nikon Micro-NIKKOR-P Auto f/3.5 55mm lens, don't you agree? There is hardly a mark on it, the black paint has a deep lustre, the color of the numbers is still vivid.
Now you look through it and...
...shock, horror!!! What a sight?! A gruesome fungus growth.
I was very disappointed when I first saw this, but after I picked myself up from the ground I reminded myself that this type of fungus is actually not too bad - it should clean off relatively well. For I know from experience, that fungus with long 'tentacles' - the bushy type - might look scary, but is actually less harmful than the smallish spotty kind, which is more likely to eat itself into the glass and leave a permanent mark. So, I set out to take apart the lens and exterminate the beast. (The lens had to be disassembled, because, as you know, Murphy never sleeps; the fungus took up camp inside, near the aperture blades, not on the outside surface.)
Challenge number one: unscrew the front retaining ring and remove the front lens element. It seemed easy, but turned out to be quite difficult, even though I had the right tool. (The tool being a set of rubber cones specifically made for this purpose. You can see them lined up at the top of the next picture. I picked these up on a trip to Japan in an amazing hobby shop. Recently I also saw these in Micro-Tools' online catalogue.) In the deep inside of the lens barrel there are several candidates which look like the ring to unscrew. Which is the real one? After much trying, the ring just above the lettering gave way and started to turn. I should note, that I also used some methylated spirits to try to loosen up the rings. This was applied to the areas where there appeared to be a gap between two rings, although it was hard to tell where such a gap was due to the pattern on the inside surface of the lens barrel.
The ring (or cone) I removed from the front had the front lens element attached to it. It could be further separated into two parts giving me two lenses, as you can see on the picture to the left of the screwdriver. I put these aside to clean later together with the rear lens element.
Challenge number two: disassemble the rear of the lens. While it is theoretically possible to remove the rear lens element without taking the lens mounting ring off, my tool did not allow me to get a good grip on the rear lens ring that way. So I unscrewed the five screws that held the lens mounting ring. Be warned, that these screws are usually very tight (as on the other Nikkor lens I repaired), so be careful and use a good fitting screwdriver. (I note in passing that while I was wondering how to go about this job, I took off the rubber finger grip and found, as I expected, that some screws were hiding under it. These held the focusing ring, which I also took off to give a good clean, but that is not part of fungus removal, so I won't detail that procedure here.)
When you remove the rear lens element, place the tips of your spanner wrench tool into the outer ring's slots, not the innermost ones. Better still, use a piece of rubber to take hold of the ring. If the ring is not screwed in tight, this might be sufficient and you can avoid accidentally scratching the metal.
Now that the lenses are out, we can start cleaning them. My favourite fungus killer / remover is ammonia. It does a wonderful job. Make sure you rinse the lenses well afterwards. You can also use the usual lens cleaning fluids to give a final clean. Dry the lenses well before putting them back into the barrel. Moisture trapped inside the lens is detrimental.