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Half fogged rear element group Nikor AF20mm F2.8D...


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#1 dave's clichés

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Posted 24 February 2017 - 01:27 AM

Hi guys,

             (Sorry for the preamble)  I grabbed my old AF20mm F2.8 lens with the D750 and went over the other side of the river to take a few shots of the cutting down of more dying"platanes" trees, which unfortunately are infected by a disease called "le chancre coloré" a sort of mushroom infection. Unfortunately this will kill  42,000  platanes which were planted 200 years ago both for reinforcing the canal du midi's canal banks as well as providing some shade for the horses which pulled the barges before the motorization of canal traffic, this is not counting the millions of other platanes which are everywhere in France.

  Briefly, by the end of next week there will practically no trees left near me and in the next two years all will be denuded along the canal du midi from the med to Bordeaux.....very sad indeed!

   Strangely the infection was brought into Europe in 1944 when invading Italy, from the US wooden munition cases and slowly the disease has worked it's way across Europe and has taken this long to get here 73 years no less, there is talk of a treatment for the disease but it's too late for the canals platanes.

 

  Excuse me guys, I digressed!  :huh: Anyway I took a couple of shots and was immediately surprised at the lack of contrast, on arriving home I shone a torch through the lens to find haze, last time I shot things looked OK.

 I jumped in and removed the rear element group to find the haze within, the rest of the lens looks reasonably alright. I had to make a tool to open the rear element assembly hoping to give the group of four a quick clean up, but it was the lens cement that was the culprit.

  Now I need to separate the couplet with a view to re-cementing, have any of you guys ever done such a thing, what method is used, is it done by warming or some sort of solvent? The rear group is only maybe 14mm in diameter so we are not talking about a large surface, some lens cement will also have to be found.

 I know many will say that it's a job for a professional, but I have little to lose as although the lens still functions in it's current state I don't envisage myself shooting with it, other than that I would have to find some a replacement rear group, not easy to find no doubt.

 

Tips from you guys would be welcome, BC, Klaus, Markus or any other experienced or knowledgeable folk! 

 

 Thanks in advance!



#2 JoJu

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Posted 24 February 2017 - 10:42 AM

I would be one of the "leave that to professionals"-advisors, but nonetheless, thank you for bringing these platanes to our attention. I don't know, but platanes to me are the most french trees. I see them in Alsace, in Midi, they belong to public places and canals. It's really sad if they are so sick they have to be cut.


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#3 Rover

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Posted 24 February 2017 - 11:09 AM

Since the lens is still current (I think???) or discontinued very recently - certainly not before the advent of the 20/1.8G - it's probably still serviced, and parts can be found. I would've left the entire job to the service workers, but since you've already gotten to it, I'd say things are more complicated now...



#4 dave's clichés

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Posted 24 February 2017 - 11:42 AM

I would be one of the "leave that to professionals"-advisors, but nonetheless, thank you for bringing these platanes to our attention. I don't know, but platanes to me are the most french trees. I see them in Alsace, in Midi, they belong to public places and canals. It's really sad if they are so sick they have to be cut.

  Yes a huge catastrophe about platanes JoJu, however there is talk of a insecticide, but apparently they have to treat the roots, last time I heard they were talking about about 100 liters per tree so it will cost zillions to treat. it is passed by water contamination, hence the rapidity  along the canal du midi. It is also a zone inondable here so every ten years or so when it floods a huge area is contaminated. 

 The last couple of years the hire boats have been ordered to carry an insecticide dip for the mooring ropes, all to no avail of course.

  The trees are being replanted with some form of oak trees said to be very resistant, all this is being funded by the EU.

 

 The couplet is currently bathing in acetone following research on the net from various "experts" who do this on a regular basis, another way is to heat the lenses in an oven at 300° F, for obvious reasons I didn't fancy that method.

 The lens was bought cheaply for 150 euros because of slight marks on the rear element, it's IQ was fine then and I thought I had a bargain, I'm sure it wasn't a problem of lens storage here as I keep my lenses in lightly heated "safes", two halogen bulbs just raise the temperature so as not to risk condensation as well as reusable silica gel packs, you know belt and braces method, so it came as quite a surprise, all my other lenses are fine, so this lens had "history". 

  I will ring Nikon but my guess is they will not sell me the spares and will insist on me sending the lens in, that will no doubt cost more than the lens is worth on the S/H market, a better idea is to sell the lens on ebay declaring the fault. I've been looking and lenses for spares or whatever still make reasonable money, I'll see how I get on!



#5 JoJu

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Posted 24 February 2017 - 11:54 AM

Alright, if you already dissolving the Canadian Balm, you can as well polish the rear element (tooth paste should do, but no whiteners...) and but the multicoating back by heating some crystals in a frying pan and put the lens in that steam. Vacuum is overrated anyway

 

Just kidding...  :huh:

 

:D



#6 dave's clichés

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Posted 24 February 2017 - 11:55 AM

Since the lens is still current (I think???) or discontinued very recently - certainly not before the advent of the 20/1.8G - it's probably still serviced, and parts can be found. I would've left the entire job to the service workers, but since you've already gotten to it, I'd say things are more complicated now...

 Whether the lens is still being produced I doubt, but it's certainly available new and is listed. Nikon have a nasty habit of charging 300 euros for anything that needs anything... plus postage, there's plenty on the bon coin for €200 and mine is not the prettiest example on the planet. €300 was the quote I got for a replacement VR on my AF-S 70-300 VR with postage around €340, they are available new at that price.



#7 dave's clichés

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Posted 24 February 2017 - 11:58 AM

Alright, if you already dissolving the Canadian Balm, you can as well polish the rear element (tooth paste should do, but no whiteners...) and but the multicoating back by heating some crystals in a frying pan and put the lens in that steam. Vacuum is overrated anyway

 

Just kidding...  :huh:

 

:D

Actually steam is not a bad idea, I'll have a cup of tea and a couplet for breakfast with a bit of ketchup for the coatings!!  :P



#8 dave's clichés

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Posted 25 February 2017 - 08:56 AM

 Well that's over a day and a half that the couplet sits in acetone and really it doesn't look as if the lens cement is affected by this solvent, although it does look a little less hazy. Other internet advice suggests xylene which is a more volatile solvent to more resistant glues/paints etc.It looks as if this is not Canadian balm, but the epoxy based Vitrelite. In theory pure epoxy has no known solvent!

  If I get nowhere there maybe the next step will be boiling it in water to soften the glue, we are in a softly softly situation here.



#9 Brightcolours

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Posted 25 February 2017 - 09:11 AM

I'd try the oven (not pre-heated and not fast heating up). If it is expoxy based, heat does nothing though.

If all fails, you can try order this group of elements?

 

 

http://jimshomeplane...m/lensglue.html



#10 JoJu

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Posted 25 February 2017 - 09:33 AM

Even if you can part the couplet into lenses: How do you clean the lens? And more important, how do you glue them together perfectly centered and with no dust in between? Sure, it is a good strategy doing one step after another and don't pay too much attention to upcoming problems. If there's no alternative to that and no time to do complex research of get some help out of the internet, why not?

 

This is the way French nuclear power stations are realised  ^_^ no? We talk about the waste when we have it, we talk about disposal of the building when we need to wreck the first one (GoodyBye Fessenheim), maybe we can shoot it to Mercury until then. Hey, I was a young person demonstrating against the stupid stuff and now I actually read in the news "due to too much disasters, we close it down". It might be a strange sample but sometimes thinking it to the end doesn't cover all eventualities but can indicate a possible waste of resources.

 

Get another lens like that with a scratched front element and exchange the rear one with yours. It's no shame to step back from a project or find another solution.



#11 dave's clichés

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Posted 25 February 2017 - 08:37 PM

I'd try the oven (not pre-heated and not fast heating up). If it is expoxy based, heat does nothing though.

If all fails, you can try order this group of elements?

 

 

http://jimshomeplane...m/lensglue.html

 

I'd try the oven (not pre-heated and not fast heating up). If it is expoxy based, heat does nothing though.

If all fails, you can try order this group of elements?

 

 

http://jimshomeplane...m/lensglue.html

  Thanks for the link BC,  the trouble with these chemical products these days is there are so many laws against transporting them, then there are solvent laws because of solvent abusers!!  

 

  You have a nightmare of a job buying a liter of oil paint!

 

 

 

  Oh onward and upward, or was it downward? 



#12 Arthur Macmillan

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Posted 26 February 2017 - 09:19 AM

Canada balsam, I don't think has been used much in modern lenses.  According the Wikipedia (I don't have the link) it has been phased out since the end of WWII due to thermal instability among other reasons.  I think I tend to agree with JoJu.  If you can find a defective lens with an intact rear doublet that would be ideal.  So my dream of fixing my 80's era lens with a little separation are probably just that.



#13 dave's clichés

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Posted 26 February 2017 - 01:28 PM

Hi Arthur,

               BTW. I posted a link to a focus breathing video and how to test for it  and get round it on just talk page!

  

  Looks like modern glues are used in the Nikon, these later types have all the disadvantages of not being able to de-cement the elements while still having the drawbacks of misting.....a neat trick from Nikon! :o

  However I busied myself with a less stressful DIY  job.......the "Toast cooler"  I get the impression that it's maybe the first of it's kind!

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#14 JoJu

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Posted 26 February 2017 - 01:43 PM

That' what the world just was waiting for, dave! Can you do this also in birch, bamboo and redpine?

 

Now I iunderstand your efforts a bit better, you need to keep yourself occupied with interesting DIY. How about of developing a real cool geared tripod head? The available ones have all kinds of disadvantages and I'm not talking about the price tag... 



#15 dave's clichés

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Posted 26 February 2017 - 02:34 PM

 I finished this adapted tripod mount about two weeks ago, it just slots into the camper window blind frame, I've been using it for shooting small birds in the tree 3 meters away, sorry that there's no gearing....as yet! I also have a complete roll of camouflaged cloth which covers the side of the camper 20 square meters of it.

 

   The hunting season finishes in two days so I can finally go out birding etc. with out having to pick lead-shot out of my butt!    Ouch.... :o

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#16 dave's clichés

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Posted 06 March 2017 - 06:30 AM

Update on the ill fated AF20 F2.8D lens:

 

  The couplet has been soaking in acetone  for a long while, then nitro-methane, then xylene,  all to no avail.

 

  This modern lens cement is resistant to all those solventst!

 

  "Le chlorure de métylène" (I've already forgotten it's English name) seems to be my last hope, albeit small. The product is available in France in what they call "Drogeries" a sort of hardware store, the trouble is most of these stores have slowly but surely closed down and this product has fallen out of popularity. I've rung around but as yet have not been able to locate a source.

 Having ascertained that the cement isn't and probably hasn't been Canadian Balsam for some years this puts these sort of repairs out of the reach of amateurs as well professionals (the latter being uneconomical).

  I've decided not to take the heating route, as JoJu said, "if you can't dissolve the cement your unlikely to be able to clean the elements".

     In all the years of looking on ebay and the like, I've yet to see a S/H version of this lens come up for spares, maybe this "rarity factor" will put my example in good stead for someone looking for one to exchange his front element or some other part.

  

 

 BTW. Reading around the few specialist sites out there, indicates that fogging is often caused by contamination of the glue at the point of manufacture, taking years to appear. A lot of the older D series Nikor zooms have suffered from glue related delaminations, looking with LED torch shows this up very quickly. 

 

  Oh well, a pity!



#17 JoJu

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Posted 06 March 2017 - 09:20 AM

If it comes worst, some of your hard core chemical experiments did a good job hardening the glue.

How likely you will find soon a repair lenes on eBay? How likely this will have a - surprise - fogged rear element?

I think if you like to excel in stubborness you can go as well the full path and ask at lensrentals if one of their 20/2.8 D is broken but has a functional rear element.

#18 dave's clichés

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Posted 06 March 2017 - 10:42 AM

Hmmm ....Lens rentals, if they still rent such an old lens?...maybe they have a bow full of old D series bits and bobs. I could always send them an email I suppose. Yeah I'll do that later..thanks for the idea!

 

  In the meantime I'm filming the tree cutting opposite me, I'm using the D750, never filmed with it before, learning as I go, I hope to put a clip on utube when I've worked out how to edit and upload..hey ho!



#19 JoJu

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Posted 06 March 2017 - 11:36 AM

https://www.lensrent...n-20mm-f2.8d-af

Bonne chance with filming! If you ever consider a better microphone, do yourself a big favour and look outside of Nikon. Røde has some nice ones...

#20 dave's clichés

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Posted 06 March 2017 - 08:09 PM

  Ok at $49 per week I guess you could say I've had my moneys worth then!  I've had it for over a year and a half, as it's still current on Lensrental's site, I can't imagine they want to sell there "spares supply", not to worry!  

  Perhaps I could rent some of my lenses.

   Oh I sold the Pentacon bokeh monster today, actually made some money on it.....like about 3 euros per hour in terms of my labour, no getting rich there then!  :( Time to trim down on having too many lenses, like lens pruning!
  How's your Tammy G2 doing? I'm still loving mine, you have to stop down a little @ 600mm otherwise it's sharp all the way.

  A few egrets having fish for dinner..

 

https://www.flickr.c.../124690178@N08/

 

  As for a mic, I'd bought a cheapie from ebay with a "dead cat" on it  :P  It turned into a real hooligan of a wind this afternoon gusting 80-100 Kph so even the "dead cat" couldn't  tame the wind noise. I'm still struggling with Avidemux.....saving settings......

 

  Hey ho! ..  no rush!






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