20 mm AFD needs an internal part

[Matthew Currie]

I have an odd problem with a 20/2.8 AFD lens.  My wife got it many years ago for her F100, and it's been sitting unused for some time.  I recently took it out, thinking it might make a nice mild-wide lens,  and found that it had clouded up very badly inside.  I took it to the repairman, who found that an internal element that consists of two lenses glued together has clouded up inside, and there seems no cure for it.  He still has it, intending to put it back together and to look for the part number in case I want to hunt one down.  I'm guessing that it would be an unproductively expensive repair from Nikon, if they even still have the part, though I might contact them just to be sure. 

But in the mean time I figure I'd ask here, first if anyone has any wisdom on this, and second whether anyone knows of a source for either the part or for a terminally broken example of this lens, from which the part might be gotten.   

[longzoom]

There are 2 main groups of optical elements: in the front of the aperture, and at the back of it. Which one is affected?

[Matthew Currie]

There are 2 main groups of optical elements: in the front of the aperture, and at the back of it. Which one is affected?

I'm not entirely sure.  I think it's the ones behind, but would have to check. I was at the shop today and the repairman showed me the part, and I'm pretty sure he said that when he puts it back together he will do it from the rear.  I don't have the lens at hand.  It's not the one at the very rear, I know, and I don't yet have the part number for the pertinent element.

Edit to add:  the part in question is a small one with two glass elements of the same diameter glued together, which looks like the pair third and fourth from the right in the diagram shown here.  I don't see any others it could be:


https://photographylife.com/lenses/nikon-af-nikkor-20mm-f2-8d

[longzoom]

There is a tightened nut over the very last element on the rear. Do not unscrew the whole rear optical block (in some case the block needs to be unscrew, not big deal!).  Tell your technician to unscrew the nut, remove optical elements. If it is cloudy only, it could be cleaned out at ease now. In unfortunate case if the glue is affected (fungus!) nothing to do, but look for spare.  Good luck!  LZ

[Matthew Currie]

There is a tightened nut over the very last element on the rear. Do not unscrew the whole rear optical block (in some case the block needs to be unscrew, not big deal!).  Tell your technician to unscrew the nut, remove optical elements. If it is cloudy only, it could be cleaned out at ease now. In unfortunate case the glue is affected (fungus!) nothing to do, but look for spare.  Good luck!  LZ

Unfortunately, this is what the technician found. He's already had it apart. The element in question is a glued-up pair, and the glue is completely clouded - more or less evenly throughout. It's odd because the lens is otherwise quite clean and free of fungus.  The only cure he's suggested is either to send it back to Nikon or to find a new part,  which he hopes to get the number for.  I'm sort of  hoping once I get the part number, I can do a search, and maybe find it from a dead lens, but I figured there's no harm in asking here, as there are plenty of lens experts in the room, and who knows what might be lurking in someone's bin?

[Nasos Kosmas]

It’s not a glue, most of the times they put some kind of resin to hold the lens together, if your technician treat with some heat it will be apart ask Richardhow or search the blog

[Matthew Currie]

It’s not a glue, most of the times they put some kind of resin to hold the lens together, if your technician treat with some heat it will be apart ask Richardhow or search the blog

Thanks for that.  I'm kind of hoping Richard Haw chimes in here, but have not yet rummaged in his blog.   However, I suspect that a replacement part will be more reliable if it can be done. 

[Erik Lund]

It's always fun to tinker with lenses, but it's not cheap


Trying to fix an old lens like this one will most likely end up being more expensive than buying a second hand sample unfortunately,,,


Also getting the lens to perform again is not something that is granted.


In the old days elements where glued together using 'Canada Balsam' today the industry has shifted to using clear UV curing Epoxy.


Canada Balsam can be dissolved of you slowly heat up the elements i a pot of water.


You can get glass clear Epoxy as a two component set to re glue the elements, super difficult, I have only done this on two lenses, super difficult to do without air bubbles. Centering the elements and keeping them fixet in position while the gule hardens is another challenge,,,!


That is why they use UV curing now,,,

[Marco Lanciani]

I had the same lens and same issue... I went to the local Authorised Nikon service in Rome and they replaced the affected lens group. There is no other way.
It costed me almost €300...  but you can still sell the lens on ebay, optically in excellent condition, for the same amount. They also clean the lens inside, so no dust, no particles... better then new. 

Same issue with the AF 180mm 2.8D... same solution. But only €200 
This last one is a great lens, I still use it and I'll never sell it... at least till Nikon will replace it with something that is worth it.

The repairman told this is pretty common behaviour with AF 20mm and 180mm 2.8D lenses... If you have one of this lenses, you can expect this to happen, sooner or later...

[Matthew Currie]

I had the same lens and same issue... I went to the local Authorised Nikon service in Rome and they replaced the affected lens group. There is no other way.
It costed me almost €300...  but you can still sell the lens on ebay, optically in excellent condition, for the same amount. They also clean the lens inside, so no dust, no particles... better then new. 

Same issue with the AF 180mm 2.8D... same solution. But only €200 
This last one is a great lens, I still use it and I'll never sell it... at least till Nikon will replace it with something that is worth it.

The repairman told this is pretty common behaviour with AF 20mm and 180mm 2.8D lenses... If you have one of this lenses, you can expect this to happen, sooner or later...

Thanks. That's interesting to know.  I got the lens used some years ago for what seemed then quite a bit, but is probably less than it would cost for Nikon to repair it, so I suspect it won't be fixed in a hurry unless I can find the part separately, as the lens is not at the top of the list of lenses I need to use.

[Matthew Currie]

A temporary update:  I got the lens back from the repairman who got me a part number, and suggested that if I want to pursue it I might be able to find something on Ali Baba in China.  I did some hunting, found a part number reference from AliExpress, and it looks as if a part is on its way from China.  I don't yet know what's going to turn up at my door, or when, but something is happening.