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09-19-2008, 10:18 PM   #1
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Lens assembly

As my last post, I got a TEFNON 70-200 Marco lens from my dad. It is a very old one and I found the fungus in the middle of the lens. So I decide to fix it. The worst scenario is ......., there is no worst actually.

Here is my suggestion if someone want to do the same.
1. Get the best tool set. $19.99 from Canadian Tire doesn't work. The screw on the lens are soft and weak, they are made by aluminium (I guess). If you cannot pull it out, you probably will not forever.

2. Try to be organized. Remember where all the screws coming from, and put them back to the same spot.

3. Glove and clean paper. I found it is almost impossible to make the lens perfect clean. The clean paper can only be use once. Otherwise, the fibre of the paper will stick to the lens.

This is my first long post. Hope enjoy.

#1. Picture before the fix.


#2. After fixing. wide open


#3. 200mm, wide open, 100% crop,


#4. 200mm wide open, 100% corp.


#5. 200mm wide open 100% corp.



Last edited by ohce; 09-19-2008 at 10:37 PM.
09-19-2008, 10:20 PM   #2
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The most important picture I forgot to post.
09-19-2008, 10:59 PM   #3
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wow, congrats on getting it back together! I've taken several cheapo (already broken) lenses apart, but I've never been able to get the back together again....
09-20-2008, 01:32 AM   #4
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Ive dissasemble three lenses (Chinon 50/1,7, Zenit Helios 58/2 and Pentax-M smc 55/1.8) and managed to get them back. Chinon was opened and cleaned for some dust, Helios was opened just for fun and smc 55/1.8 was opened for fungus, but I didn't manage to dissasemble all of glass. Actually, I'm having problem with front and back elemenst, which are tighten together and I just couldn't separate them... and fungus is just there... Any hints?

09-20-2008, 04:49 AM   #5
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A well desreved congrats, ohce.

I would like to know
1. How did you remove the front - what tools did you use?
2. What order did yuo follow - did you start at the back or front.
3. What chemicals did you use to remove fungus?
09-20-2008, 11:39 AM   #6
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For the front element, please see the picture. For my case, there are 3 tiny screws that tighten the front element. As long as you loose them, you can screw the element out of the external tube. Also, I found this is the way that we can use to adjust focus issues.

Hope it helps.




QuoteOriginally posted by Spex Quote
Actually, I'm having problem with front and back elemenst, which are tighten together and I just couldn't separate them... and fungus is just there... Any hints?

Last edited by ohce; 09-20-2008 at 12:17 PM.
09-20-2008, 11:50 AM   #7
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Thanks, JCSullivan. Here is my answers.
1. See the pervious post. I brought a screw driver set ($19.99) from Canadian Tire. After I use it, I feel it is not as good as I expected.
2. See attached image.
3. The cleaning wiper (Wet) that come with LCD Screen protector.

Hope it helps.



QuoteOriginally posted by JCSullivan Quote

I would like to know
1. How did you remove the front - what tools did you use?
2. What order did yuo follow - did you start at the back or front.
3. What chemicals did you use to remove fungus?
09-20-2008, 10:01 PM   #8
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QuoteOriginally posted by Spex Quote
...and smc 55/1.8 was opened for fungus, but I didn't manage to dissasemble all of glass. Actually, I'm having problem with front and back elemenst, which are tighten together and I just couldn't separate them... and fungus is just there... Any hints?
Acetone is a good solvent for the glue used to lock the rings holding individual elements together. Let it soak for a few minutes. Make sure you have a decent tool that fits well into the slots to unscrew the rings.

09-21-2008, 05:02 AM   #9
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Thanks for the hint, but will acetone mess up coatings on the glass?
09-22-2008, 11:32 AM   #10
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QuoteOriginally posted by Spex Quote
Thanks for the hint, but will acetone mess up coatings on the glass?
I have used acetone on Pentax lenses with no problems so far. With any solvent, I try to use the minimum strength and quantity that will work. I also look for lenses that have cemented elements (Bojidar Dimitrov's page has optical diagrams that show this) because I don't want to dissolve this glue, whatever it is. So far, the only thing I have ruined with acetone is lens caps. I use mineral spirits for cleaning oil off aperture blades and denatured alcohol for other cleaning.

I have heard that some old lens coatings are vulnerable to solvents, but in my experience, Super-Takumar and newer coatings are OK.
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