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Uncleanable lenses
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PostPosted: Mon Aug 06, 2012 4:48 pm    Post subject: repairing lenses... Reply with quote

I have been holding a 400mm vivatar 5.6 prime that needs internal cleaning. I have been looking for a schematic.

what i am really looking for tho on here is a where can I find lens rubber grip. Id love to modify the look of my lenses with older style rubber if I can find it. I hate the waffle rubber of the late 80 and 90s. does anyone know or have experience with it?


PostPosted: Mon Aug 06, 2012 6:01 pm    Post subject: Reply with quote

Carl Zeiss Jena Sonnar 135mm f/3.5. Easy to disassemble but very tricky to put back together. Bought one, fixed stuck blades and wasn't able to put it back on properly again. Please don't do it!

Yashica ML 28mm f/2.8 has unreachable front element, it is cemented and you can only reach it's back slightly from behind after disassembling the front end. Any front element dirtyness won't be easy (if possible at all) to clean.

Jupiter 37AM 135mm f/3.5 also has a cemented block which makes some elements impossible to clean.


PostPosted: Tue Sep 25, 2012 2:05 am    Post subject: Reply with quote

inombrable wrote:
I've cleaned and totally dissasembled three series one 70-210, first one is mine and the other two i sold, everything worked perfect (took me a while but it worked)




Could you answer a question about the tear down and rebuild of the three Vivitar 70-210mm lenses, please:

Were you attentive to collimation issues during the process? Did you see this as an issue?

I have one of those lenses which needs cleaning and rebuilding. I don't even know if collimation is an issue with that lens, it is so old (mine is, anyway) that collimation concerns might not even be appropriate or apply.

But the need to mark each element's rotational position before disassembly . . and then duplicate those same relative rotational positions upon reassembly strikes me as intensely burdensome . . unless it also is mandatory. I work strictly at home and do not have here the equipment to perform lens collimation from scratch. My only way to attend to the matter is to try to duplicate what the factory did when the lens was originally manufactured. I know with certain lenses it's an issue and with others not. But I don't know which are which.


PostPosted: Mon Aug 12, 2013 9:07 am    Post subject: Reply with quote

CZJ Flektogon 4/50 first version zebra - it has front group in metal cartridge with rolled edges. The cartridge can not be disassembled.


PostPosted: Sat Feb 15, 2014 8:22 pm    Post subject: Reply with quote

As suggested by pros (from the local ex-military optics plant), a equal part mixture of tetrohydrofuran, metyletilenketone, cyclohexanone and acetone, when applied in 60C warm bath for 1 hour, will unglue 99% of cemented lens elements.

If you have no idea where to get these cryptic named chemicals, the above mentioned mixture can be bought already as NSF primer for PVC pipes, like this: http://www.amazon.com/Oatey-30750-Listed-Primer-4-Ounce/dp/B000L8DMKQ/ref=sr_1_fkmr0_1?ie=UTF8&qid=1392495109&sr=8-1-fkmr0&keywords=oatley+nsf+primer (Just do not forget to look in MSDS for mentioned chemicals and avoid colored mixtures - might leave tint on lens!)

But use it with extreme caution! this stuff is terribly poisonous when inhaled and easily flammable. So I suggest to use it only outdoors, wearing protective glasses and all necessary stuff.

Regarding the fungus, another suggestion from pros, this time - biologists.

Fungus is the living tissue, so applying vinegar or alcohol does no harm to it at all. While it may wash away fungus from surfaces, it does not kills spores, in fact, fungus can use both vinegar or alcohol as feeding supply (and even above listed poisonous concoction might not be able to break fungus spore cell). Only way to deal with funguss is to break it's cells, most commonly used and easily to get solution is sodium carbonate, available in stores as washing soda. Of course, more exotic alcalis or even gamma rays can be used, but they are less available for home users.


PostPosted: Sat Feb 15, 2014 11:41 pm    Post subject: Reply with quote

hk300 wrote:
Today i talked to a lens repairer and he has heard that some of his old collegues (pity is that he dead several years ago) you could 'cook' the glued lenses in oil (around 200C ) and then the lenses would seperate after some time. Then he used Canadian Tree Balsam to glue the lens element back.

Anyone knows more about this method?


Canada Balsam (CB) is also used as a mounting medium by microscopists to permanently mount specimens.

The solvent for Canada Balsam is Xylene (or Xylol as its sometimes known). The name suggests that it is distilled from wood extract. It's probably better than boiling in oil (type not specified) .I think xylene is not normally used these days as acrylic mounting mediums are 'safer' but I'm sure it can be obtained. New CB will probably come from the same source.

The use of a different 'glue' will alter the refractive properties of the lens. The original lens formula will have been computed to work with CB. The stuff between elements (in old lenses) that yellows or sometimes appears crystalised is almost certainly Canada Balsam.

If you want to unstick CB use xylene. Keep it away from plastic.

I havent unstuck lenses using xylene but i have managed to deconstruct victorian microscope slides sucessfully.


PostPosted: Wed Mar 05, 2014 6:49 pm    Post subject: Reply with quote

Petri 200mm/F4 prime.

The front element consists of two glued elements. Often that glue disintegrates, looking like just someone sweeped with dirty cloth on the lens, so you might think that it is easilly cleanable. It is not, and also, these two elements are mounted press fit in metal ring, almost impossible to disassemble.

Photos coming soon.


PostPosted: Fri Aug 01, 2014 12:06 pm    Post subject: Sigma 400mm 5.6 MF Reply with quote

Prone to haze between the elements of the front group, from browsing around online. This is what the front group from one i got looked like!



I consulted Eddie "the Lens Doctor" Houston by email.

Quote:
I have tried on numerous occasions to re-cement doublet element groups, and never had any success, you will find if you do manage to separate them without any scratching, where the air has entered the cement there will be glass discoloration, and trying to polish this out distorts the glass, even a fraction out and it is no good, so I have given up on trying to repair separation ..........best of luck ..


PostPosted: Tue Dec 16, 2014 4:05 pm    Post subject: Reply with quote

I tried using jewellers rouge and a gem polisher to take off haze see this thread.
http://forum.mflenses.com/hazy-lens-element-not-responding-to-normal-cleaning-methods-t66075.html