If you can get in there and clean them yourself you'll find, the fungus has usually eaten away at the lens coatings, so depending how much you love that lens, you may not want to go there.

Cleaning a lens is a very complicated thing to do if you've never seen it done before.

Primes are simpler than zooms. There is often a central cluster of elements with a fixed front element and a rear element, if the fungus is in-between, it might not be that tough to get to and clean.

Nikkor AIS fit that description and you can forget about taking the central cluster apart yourself.

Sometimes there are 2 elements glued together and the glue yellows with age (or exposure to heat) or fungus grows from the outside to the inside on the glue.

I've had this happen on an old Leica M lens and I was able to buy just the affected front element from a dealer in the USA. A Swiss dealer told me parts for the old lenses aren't available. The US price was good so I didn't bother to look in Germany where the lens was made. The Leica LTM mount lenses are simpler than the Japanese lenses. I googled and found some pages of a book on Amazon that were viewable on the internet and it was enough to let me clean the focusing mechanism on my Leica LTM lenses, however they a re a really simple 1930's design. The front element I had replaced by a lens tech.

Specifically getting it back together so that is focuses properly is an even greater challenge than taking it apart and usually left up to a professional lens service. Your local photo shop maybe able to point you where to go or you could try some of the bigger lens services that have an internet presence like Duclos or Whitehouse A/V in California Visual Pursuit in Ohio, The photo district (many stores and techs in NYC) as wells as some good ones in the UK.

You could always buy a junk lens of the same type off ebay, take it apart and learn how it goes back together. A spanner wrench and good set of precision jewelers' screwdrivers are needed (not the junk ones for $3 at your local hardware store)

Any professional rental house or shop selling lenses has a lens tech working for them somewhere, and if you can go to them directly then you can save some money. If you ask around and see an old man in the back with a bench neatly maintained with lots of little screw drivers and bottles of fluid, take a lens to him: the old timers are usually good and may not be too pricey. I can recommend a great Inventor/Camera Repair/Lens Repair Technician in Switzerland if you want. I wouldn't recommend it if you weren't nearby, since Switzerland is not in the EU (customs & insurance issues).

Another great service is in the EU, in Braunschweig, called " Classic Fototechnik".

@simurg the iris blades are extremely fragile, handle with care! Disclosure: I only once took a lens apart, but, watched a pro (a friend) do it many times.

Where are you located?

Some fluids can be corrosive and remove the coatings on the lens (those coatings are fragile!). Isopropyl alcohol can remove paint and there are 2 types 70% and 99%, I believe. I think you generally want 99% or the purest you can get, but you had better get a better recommendation that what my vague memory remembers at this point. I've also seen lighter fluid used, but, can't recall if it was on optics... or maybe it was lighter fluid on optics and iso alcohol on everything else. I don't know for sure.

Someone else should chime in here or you should do some googling.

@RRRR would like to hear more about what types of lenses you have been able to work on and what your resources for info are.

My lens tech friend showed me how to de-click a Nikkor AIS lens, but, I have yet to do one myself. I have recently moved and don't have a good work bench yet.

He had to use some adhesive remover on the 6 or 8 tiny screw on the rear mount to get them loose. Yes, nikon glued their screws in place. Today loc-tite is used instead.

As Others have said it depends what lens you want to clean.

I cleaned an older Nikkor 85mm F2 AIS which had a bit of fungus around the edge of the front element. Worked a treat and the fungus had been in there for years and was bugging me.

I also Repaired 3 Nikkor 55mm f2.8 AIS Micro lens that were getting binned from work. It was impossible to focus them as the grease had dried up found a nice tutorial on line step by step now they all work fine.

The one Other Lens that was getting binned And I am stuck Fixing is a nikkor 105mm f2.8 AIS. Again dry grease and don't have a clue with this one.

So Just because you can repair one lens does not mean they are all the same.

Did destroy a nikkor 70-200mm lens it was a newer auto focus forget which, but be warned its not for the faint hearted lens repair

Craig R

@CFreak the easiest thing, and highly necessary for most repairs (unless you know the design type well) is to find a guide online for a specific lens. You have to do a bit of research and make up your own mind wether you want to go ahead.

Flektogon 35mm mc are notoriously easy to service + they have an easily accessible helicoid that still has a similar design like many other vintage lenses = a good place to start for understanding how to disassemble and reassemble helicoids.

I did a full service on a meyer optik 135mm f2.8 that had a stuck aperture blade. It took a while, in particular the helicoid was a bitch to put together since I did not take enough care during disassembly.

I would not go into something too complicated as I don´t have any proper "shop" to work in, nor do I have all the proper tools, like wrenches for retaining rings. (I use calipers instead = a bit risky).

@RRRR, the meyer optik would definitely be a lens worth taking time to service! Love that bokeh monster..

On that note, if you do need cheap lenses for test diy take aparts, try searching for old 135mm f2.8 lenses (many brands to choose from)...there's many on ebay that don't even sell for cost of shipping!
I bought a no-name Sonagar 135mm f2.8 because it had 10 aperture blades, but they were super oily and when I took the lens apart, found one of the blades was bent which threw the rest out of wack, and so now I use the lens without any blades! (super soft, but wonderful bokeh, best not in sun).

@simurg The acetone should not be harmful for real coatings, as those coatings are hardened chemicals bonded with the glass.. That's not to say that there aren't cheap lenses with some kind of sprayed on coatings that aren't fully bonded with the glass and might come off with acetone.

With that said, I have to reiterate that using acetone is great for cleaning the glass itself and the anodized aluminum parts, HOWEVER, you MUST make sure that it does not come in contact with any PAINTED surfaces, plastics or rubbers. I also only really use acetone for cleaning the lens elements themselves before reassembly. Once reassembled, I'll just use ordinary lens cleaner (usually iso-propanol) on the outer lenses. Even then, use canned air to blow any possible dust off the lens before you wipe anything on the lens! You never know when that piece of dust is actually a piece of dirt or something that can scratch your lens! Always use a new cotton ball or cleaning wipe on EVERY swipe. Once that ball has gone across the surface, it's contaminated with oil and every swipe will only smear what you picked up the wipe prior. Cotton balls are cheap, so are solvents. Cleaning glass properly can take minutes to hours per element, especially if the glass has oil on it.

The blades in older lenses are usually black anodized aluminum, as are the housings for the blades and such. If you can get the assembly out and remove the glass, you can soak the aperture assembly in pure acetone and rinse it out with clean acetone. I've also used automotive brake cleaner for these things but it can leave a residue. Just make sure that there are NO particles of grease left anywhere or it'll continue to migrate and stick the blades or get all over the glass. Try washing the assembly out before you dis-assemble if possible. Those assemblies are a real pain in the ass to put back together if you are trying to figure it out without an example or instructions.

I'd also use clean latex/nitrile gloves without the powder, you can get these at automotive parts stores too. Whatever solvent you use can actually wick the oils from your fingers into your cotton balls/towels and get grease on your lens making it harder to clean.

If you decide you'd rather use alcohol to clean the glass, make sure it's the purest alcohol you can get, preferably Iso-propanol. Other alcohols have too much water in them or, like ethanol, are hydroscopic and will absorb water from the atmosphere and cause smearing. Almost all alcohols will leave a slight residue, though.

On plastics, I might go a different route. I'll use an industrial degreaser (like Greased Lightning or others) and wash them with a toothbrush and clean water. To dry, I use canned air to blow the water off. Be careful though, you might still have residue because surfactants(the active part of degreasers) don't work as well as solvents. Don't let the parts air dry or else you'll have a lot of residue on them. Also, use gloves here too, mainly because the degreasers will dry the hell out of your hands and can actually cause your skin to shrink and crack if you let too much get on your skin! I know from experience!

How can I remove a lens's coating?

Removing the coating from just one element surface will not have much of an impact. I have a coating in bad condition, and a neutral density spot filter that I want to remove.

@svart thank you very much this detailed technical infos.

@balazer I've tried/tested cellulosic thinner for coatings. Glass was more transparent. But attention! For your hand-skin and other lens parts. Solvents is carcinogenic!! And you can get drunk!

Please watch it for smile and learn moree:

@mee is this what you meant? (Naphtha)

@tetakpatak, yes. Spelling is not always my strong point.

Laughed my a%% off! That's not the correct way to clean a lens!

1st get yourself some proper tools: http://www.ebay.com/sch/Cameras-Photo-/625/i.html?_from=R40&_nkw=lens+tool Don't use a pair of scissors, did you notice the bandaid on his thumb?

When you're done, you might want to check your lens on a collimator...