Contax Yashica 100/2 fungus cleaning

I can't say that I've ever seen a teardown and cleaning video, or even a text post or pdf about one being done. A quick search didn't yield any results either.

The 100mm f/2 isn't a cheap lens, so I'd be remiss if I didn't offer a caution in taking a DIY approach, but with that said... the issue with cleaning takes a back seat in the process behind disassembly, and the 100/2 doesn't look like it comes in the 'easier' barrel/case types, like the 35/50/135 lenses do.

I don't have one to examine, nor have I opened one before, so I can only guess which way it's constructed. I do have my doubts about simply unscrewing the front group as a whole like you can on the more common fixed lenses in the normal and wide end of the line, so that leads to 2 other possibilities. The flat front surround ring may unscrew, which would give you relatively easy access -OR- there might be multiple barrel lock screws hiding under the grip rubber, and that can be a nightmare on older lenses when those teeny 0.5mm screws crack and break, and get thoroughly stuck as a result.

If you're determined and willing to take the risk to crack open the barrel, you should be able find any number of videos on YouTube on the actual cleaning process.

One other caution when it comes to cleaning fungus... if it's old enough, it will etch itself into the glass, and no amount of cleaning will make it optically better once cleaned. If after a thorough examination - like with an 8x loupe - you see that the tendrils look 3 dimensional... it's past saving. The best you can do is use UV light to kill what's there and halt further spread. That's also a "rinse and repeat' every few years, or even less under crappy conditions.

The 100/2 has 67mm filter threads, so if the front ring can be removed you'll need to find an appropriate sized rubbery ring to press onto the lens ring to grip and turn it, without it's edges overlapping the glass of the front element. Trust me that it doesn't take much to obliterate the coating layers if they get dragged over.

I purchased a complete stack of cone-shaped rubber grips to do exactly this type of teardown, and the largest one is 61mm in diameter which works for 62mm surrounds, so obviously you'd need something considerably bigger at 66mm. My guess is that you would need to make your own or adapt something similar to work.

There's one other caveat that could come into play, and perhaps one of the other members might have some insight. If the 2nd/3rd lens on a 4/5/6 lens group is the only one to clean, those _might_ be fused into a plastic sleeve as a fully assembled stack. Those can't really be opened and resealed, so be prepared for any possibility.