Blemish inside 16mm 3.5 rear element

[Snoogly]

It was sold as ‘junk’, but it appeared to be in mint condition - until I noticed a crescent shaped blemish on the inside of the rear element.

Any ideas what it is?

I think I will need to pluck up the courage to follow Richard Haw’s maintenance guide …

[Roland Vink]

Hard to be sure. There are two sets of cemented elements in the rear, so it could be separation. If so, it will be difficult if not impossible to repair. Does the blemish change colour or disappear when viewed from different angles?

[Snoogly]

No, it keeps the same size and shape, and color

[Snoogly]

Easy enough to get into, but I am finding it impossible to separate the two sets of cemented elements. The inner one refuses to budge,

[kirillr]

Hello
It looks like separation.  I have one lookin nearly the same but in some worse condition. It's same model with same problem. Mine was bought for parts- AI ring. My technitian from SPb, Russia, former engineer from USSR military optical fabric, told me that he could separate and then clue back my but there is no need for that (because it's for parts) He successfully did that operation many times on old Leitz lenses and early Canon EF lenses. But he using the same clue(balsam) for all lenses because of balsam availability. So after repair lens may be not as it was originally. Probably in your location there is such trained technitian.

[Snoogly]

I think I will send it to this chap in Taiwan. He seems to be a master at troublesome issues like this.

http://lens-cla.blogspot.com/2014/01/nikon-af-nikkor-20mm-f28-d-lens-group.html

It was sold as 'junk' though, but non-returnable. ¥16,000 it cost me, so I'd like to do what I can get to get it fixed.

[Birna Rørslett]

Have you tried to shoot a few pictures with it? The blemish might not be apparent except for high-contrast situations.

[Snoogly]

Have you tried to shoot a few pictures with it? The blemish might not be apparent except for high-contrast situations.

I have, and they were generally rather milky and cloudy. I think the blemish may be the tip of the iceberg.

[Erik Lund]

Fixing this is not a DIY job.You can heat the elements up in water and if they are held together by Balsam cement, as I suspect, they will separate, but putting them back together clean, centered and with the correct thickness Balsam cement is near impossible.Later lenses use an UV hardening epoxy or similar.

[Snoogly]

Fixing this is not a DIY job.You can heat the elements up in water and if they are held together by Balsam cement, as I suspect, they will separate, but putting them back together clean, centered and with the correct thickness Balsam cement is near impossible.Later lenses use an UV hardening epoxy or similar.

Thanks Erik.

I was going to send it to that chap in Taiwan, but his basic fee is $150, and there would be postage each way on top of that. No guarantees he could whip it into shape either.

So now I think I will try to sell it for ¥10,000 as junk junk!

It’s a shame, but my fault for buying it as junk in the first place. A new Laowa fisheye would have been cheaper in the long run.

[Akira]

Have you tried to contact Kiitos or Hayata Camera?  I'm not certain if either could fix the separation, but maybe it's worth contacting.  The repair won't be cheaper, but you should be able to make sure whether the repair is doable.

I'm not sure if they speak English, but I could call them for you.

(FWIW, Kiitos makes it clear that at least the balsam separation of S-mount Nikkors is irreparable.)

[Gone]

If it is junk junk then it may be worth trying gentle heat on the assembly - if the basalm softened enough the blemish might disappear?

[Snoogly]

Have you tried to contact Kiitos or Hayata Camera?  I'm not certain if either could fix the separation, but maybe it's worth contacting.  The repair won't be cheaper, but you should be able to make sure whether the repair is doable.

I'm not sure if they speak English, but I could call them for you.

(FWIW, Kiitos makes it clear that at least the balsam separation of S-mount Nikkors is irreparable.)

Thanks for the kind offer Akira :-)

In fact I hadn’t considered them due to both language issues, and the fear of a high cost. Given how cloudy the photos are, are I think there is also haze inside there somewhere. A full CLA would be required.

But I think it would be worth the risk of an initial inspection, as then I could know what is possible, and what the final cost would be.

I will send you a private message :-)

[Snoogly]

If it is junk junk then it may be worth trying gentle heat on the assembly - if the basalm softened enough the blemish might disappear?

I can’t even remove the offending group though

[Akira]

Just called Kiitos.  Kiitos is a repair shop founded by the ex-Nikon repair persons.

The repair person on the phone said that the rear group of Snoogly's 16/3.5 fisheye is very probably suffering from the balsam separation.  He further explained that the rear group of this fisheye consists of two glued elements and is sensitive to the shock or any sort of force.  If such force is applied, it is prone to separate which is irreparable.

If the seller sold the lens as "junk", I would say he is at least honest.