Author Topic: Blemish inside 16mm 3.5 rear element (Read 5604 times)

Snoogly · « **Reply #15 on:** January 13, 2022, 07:22:23 »

Quote from: Akira on January 13, 2022, 07:06:43

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.

I hear you :-(

Gone · « **Reply #16 on:** January 13, 2022, 11:06:55 »

Quote from: Snoogly on January 13, 2022, 00:32:20

I can’t even remove the offending group though

Warm the whole assembly that you have removed from the lens, maybe in a warm oven?

Snoogly · « **Reply #17 on:** January 15, 2022, 07:36:59 »

Well, I sent photos of the damage to the Taiwan repair man, and he said he is confident he can repair the grouped element. I will send the lens to him on Monday, but Covid may delay its arrival …

Fingers crossed he can do it, and that it will be for the $150 he estimated.

Macro_Cosmos · « **Reply #18 on:** January 20, 2022, 03:44:29 »

Measure the thickness of the doublet. Use a good calliper set.
Use a heat plate, immerse the element(s) in a container and use low-ish temperatures. Depends on the bonding agent, around 45-50 Celsius should be adequate. Typical balsam type resin used in older lenses has a melting point of around 40 degrees Celsius. Separate it and clean up the glue, then rebond the glass with optical adhesives, Norland ones work well. https://www.edmundoptics.com.au/f/preloaded-norland-optical-adhesive-syringes/39757/

It is doable, and should give better results than a milky haze. From what I am reading, I think there are other issues as well unfortunately. I used to own one, it is an incredible lens.

Snoogly · « **Reply #19 on:** January 20, 2022, 07:14:48 »

It should be arriving the hands of the Taiwan repair man any day now, and he said he would report back to me after he has inspected it.

We shall see!!!

It’s such a hard lens to figure out what is going inside, without fully opening it up. Looking from the front it’s hard to see any issues with the glass, and looking from the back it’s hard to see further than the closest group. Inscrutable ….

pluton · « **Reply #20 on:** January 22, 2022, 02:41:10 »

Quote from: Snoogly on January 20, 2022, 07:14:48

It’s such a hard lens to figure out what is going inside, without fully opening it up. Looking from the front it’s hard to see any issues with the glass, and looking from the back it’s hard to see further than the closest group. Inscrutable ….

My copy made 2 visits each to 2 repair services (4 total) just to get re-greased, internal filters cleaned, and reassembled correctly. Inscrutable indeed!
PS: What annoyed me was not that the lens proved difficult tor professionals to service, but that it was handed back to me three times in a clearly un-repaired condition.

Akira · « **Reply #21 on:** January 22, 2022, 03:50:13 »

Special lenses such as the fisheye should be more tricky to assemble because of the tolerances tighter than, say, not-so-fast standard primes.

When I tried non-Ai Nikkor 20/3.5 (72mm filter thread) for the first time on F3, I was surprised by its pronounced barrel distortion. On the contrary, the one I finally purchased later didn't suffer from any perceivable distortion. The optics of the first sample was perfectly clean. I think that the first sample was badly assembled after it was cleaned and lubricated.

Unlike more modern lenses, the older MF Nikkors needed to be assembled by well-trained technicians using a handful of specialized tools.

Snoogly · « **Reply #22 on:** April 06, 2022, 10:02:12 »

Well, he had the lens for over two months, and I got a bit angry with him. He’s just a one man show, but two months with no news at all was worrying.

Then yesterday I received a mail saying it is fixed! No real explanation for the two month black hole of information, but I sent the $150 repair cost via PayPal, and now just have to wait …. again.