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Carl Zeiss Flektogon 20mm F4 cleaning front elements
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PostPosted: Sun Sep 06, 2020 9:55 am    Post subject: Carl Zeiss Flektogon 20mm F4 cleaning front elements Reply with quote

Hello fellow vintage lens repairers and enthusiasts,

I have a problem cleaning a Flektogon 20mm F4 M42 ''zebra'' rings.
The front elements have a really slight haze in them, only visible when shining a strong light on it.
So, I wanted to disassemble the lens, specifically the front elements.

I have cleaned and repaired Flektogon's 20mm f/2.8's before, so my guess was that it would be really easy. Just unscrew the front ring, unscrew every ring that holds an element and voilà, every single element comes out and can be cleaned. Very easy and straight forward lens.

However, with the 20mm F4 I can only remove the front ring and the first element. After the first element there is no ring with holes in it to put a lens tool or whatever. I tried my rubber lens ''unscrew'' tools and suction cups to remove the second element, but it isn't moving at all.
Also, in comparison with the 20mm f/2.8, you can't unscrew the last element of the front elements group either.

I have searched the internet and I could not find any information on how to clean the glass of a Flektogon 20mm F4.
Of course I already have the basic schematics of most vintage Zeiss lenses, including the three versions of the 20mm f4, but that does not help me with this particular lens unfortunately.

My question: Does anybody know how I can remove all other elements of the front part of the lens, without drilling and any other mechanically similar operations that ''hurt'' the lens?

100% pictures:
https://drive.google.com/drive/folders/1qiIC_mYfhaowx8PrLWEXZTRDxI9bk8V_?usp=sharing
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PostPosted: Mon Nov 30, 2020 8:49 pm    Post subject: Reply with quote

Only a guess here...

From the diagram the outer front part of the lens body can be unscrewed and separated from the main lens body, bringing along the entire front group. Then disassemble the front group from other end.


PostPosted: Wed Apr 07, 2021 11:20 pm    Post subject: Reply with quote

Have a look at this video: https://www.youtube.com/watch?v=6Tl6lhxrJr0


PostPosted: Tue Sep 05, 2023 9:41 pm    Post subject: Re: Carl Zeiss Flektogon 20mm F4 cleaning front elements Reply with quote

HackingDutchman wrote:
Hello fellow vintage lens repairers and enthusiasts,

My question: Does anybody know how I can remove all other elements of the front part of the lens, without drilling and any other mechanically similar operations that ''hurt'' the lens?

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I opened it the way it's supposed to be opened; not a single visible mark, or any kind of damage.
Shamelessly reviving this necrothread due to having looked for this information for quite a while and it isn't posted anywhere, leaving this here for others like me who might be searching for it.

Steps:
1 - Remove face plate using rubber stopper. Unscrew and remove the entire front optical block. Place the rest of the lens upside down to prevent dust falling into the lens.
2 - Don't let the rear of the optical block touch anything. Scratching that small piece of glass will ruin your lens since it's greatly magnified.
3 - Put on two latex gloves, which will a) keep the glass clean and b) work better for the next step than a rubber stopper.
4 - Use spanner tool to remove front ring. Take out and set aside the front element.
5 - The wide ring holding the next is secured with lacquer. Grab acetone (nail polish remover) and a q-tip.
6 - Apply acetone to the outer edge of that ring to dissolve the lacquer in the threads WITHOUT GETTING ANY ACETONE ON THE GLASS.
7 - Let it sit for a bit.
8 - Put your thumbs on opposite ends of the wide ring, holding the lens with your other 8 fingers on the back for counterforce and not having to set the lens down on that fragile rear element.
9 - Apply pressure (more to the outside than down or you will just fight thread friction) and apply good amount of counterclockwise force with your thumbs. The latex gives much more grip than rubber stoppers.
10 - Not opening? Repeat steps 6-9 until profit. Took me quite some strength but *pop* it unlocked and unscrewed.

The rest of the elements is held down by slotted retention rings, the regular way.

Feeling rich and lazy? Buy any of the non-zebra versions which all have slotted retention rings instead.

You can contact me at my username @ gmail.com for further questions. I probably won't read this since I signed up just for this post.

Good luck.