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09-16-2008, 02:08 PM   #16
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QuoteOriginally posted by IsaacEastgate Quote
Thanks thanks ben. I'll have to look inside the lens and see whats up, i believe it has some cemented elements, and maybe even the first lens to use aspherical elements if i remember my stuff.

Speaking of cemented elements, could it be possible that the optical glue has weakened between the elements and that they are a bit detatched, leaving squiggles where the glue has come out?
Yes, to both of your questions. The very first production lot of the Pentax 15mm had an aspherical lens. If your lens is of this very early type, it has some additional value. Pentax then found, that this was too expensive to produce at that time and went back to the original design, which was developed jointly with Zeiss and produced all later modells of the 15mm with all-spherical lenses. I think you will find the according serial numbers and some more info on the typology of the aspherical/spherical variants at Dimitrov's fantastic website.

And cemented lens groups can separate. The photograph you posted is a bit inconclusive and without further examination I am unable to decide whether this is oil on a lens (easy to clean) or whether this indicates separation. If your lens is of the aspherical type, I would get that repaired.

Ben

09-16-2008, 02:21 PM   #17
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I agree that you should not use acetone on cemented groups. The lenses I've cleaned were individual elements.

Thanks for pointing that out, Ben!
06-10-2012, 06:44 PM   #18
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I'll be attempting a repair of a Vivitar 40mm f/2.5 pancake lens this week...wish me luck. The fungus is minor, definitely in the beginning stages, and I have successfully repaired an old Vivitar 70-210mm zoom and a 28mm wide angle in the past. I'm thinking the pancake lens should be a lot simpler seeing as it only has a couple of elements?

Last edited by Judah; 06-13-2012 at 02:42 PM. Reason: Forgot a detail.
06-10-2012, 11:31 PM   #19
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The trouble with disassembling lenses is the reassembling!
In order to align the different elements, one does need a collimator.
When not perfectly aligned, the focus point will be not equal over the whole image field resulting in partial unsharpness, if not over the whole image, and/or the image might be deformed!
The smaller the lens the more delicate it is.

But, if you would take your chance anyway, then removing fungus can be done with saliva (yes the liquid from your mouth), these enzymes dissolve the fungus' organic cells.
Just keep the optical element in your mouth (cheek) for about half an hour, then rinse it with distilled water and gently dry it with a clean and soft cloth.
Then take care to orient the elements in the right direction on the optical axis...
Keep everything as clean as possible and apply oil and grease thriftily!

Good luck!

06-11-2012, 01:08 AM   #20
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QuoteOriginally posted by philippe Quote
But, if you would take your chance anyway, then removing fungus can be done with saliva (yes the liquid from your mouth), these enzymes dissolve the fungus' organic cells.
Just keep the optical element in your mouth (cheek) for about half an hour, then rinse it with distilled water and gently dry it with a clean and soft cloth.
Then take care to orient the elements in the right direction on the optical axis...
Keep everything as clean as possible and apply oil and grease thriftily!
Nice advice
Tell us how it tastes.
06-11-2012, 11:12 AM   #21
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What's wrong with cold cream ?
06-12-2012, 01:15 AM   #22
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QuoteOriginally posted by kh1234567890 Quote
What's wrong with cold cream ?
I don't know, should it be wrong?
On the other hand, what's wrong with saliva?
06-12-2012, 02:33 AM   #23
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QuoteOriginally posted by philippe Quote
On the other hand, what's wrong with saliva?
No nothing wrong. Killing fungus is the main reason.
I guess I am just hungry waiting for lunch

06-12-2012, 06:37 AM   #24
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The 'product' as used by Zeiss to 'cure' fungus is actually based on the working of enzymes, some household detergents for washing clothes have enzymes like components too.
Disinfecting with alcohol and alike is not that effective against fungus, these bacterium should be fought with microorganisms rather than chemicals, they 'eat' the fungus, not you, you are just the carrier...
BTW, that's why animals instinctively lick their wounds in order to clean and by this disinfect them...

Last edited by philippe; 06-12-2012 at 06:47 AM.
06-12-2012, 01:15 PM   #25
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QuoteOriginally posted by Judah Quote
I'll be attempting a repair of a Vivitar 40mm f/2.5 pancake lens this week...wish me luck. The fungus is minor, definitely in the beginning stages, and I have successfully repaired an old Vivitar 70-210mm zoom lens in the past. I'm thinking the pancake lens should be a lot simpler seeing as it only has a couple of elements?
If could reassemble the zoom then the pancake will be, well, piece of cake for you.

Ben
06-12-2012, 01:28 PM   #26
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QuoteOriginally posted by philippe Quote
The trouble with disassembling lenses is the reassembling!
In order to align the different elements, one does need a collimator.
When not perfectly aligned, the focus point will be not equal over the whole image field resulting in partial unsharpness, if not over the whole image, and/or the image might be deformed!
The smaller the lens the more delicate it is.
...
Then take care to orient the elements in the right direction on the optical axis...
Keep everything as clean as possible and apply oil and grease thriftily!

Good luck!
You are very right to point out the problems with collimation. In practice, though there are several things, which come to our help. Firstly, lens groups in old lenses are often marked with pencil strokes, to indicate the correct rotational position of one lens to the other. It is important to preserve and use these marks, when they are present. If there are no marks, simply make your own with a soft pencil. (Pencil is used, because it will withstand a lot of typical cleaning fluids (but no rubbing of course) and because it won't damage the coatings or glass surfaces as it does not contain hazardous chemicals (solvents etc.)
Secondly, camera lenses are all small (comparatively) and held in place quite well by centering rings and retainers, which avoid a gross assembly mistake. I find it much harder to be sure of the correct direction of the lens surfaces, than get a workable centering. Also, critical lens groups are often cemented and fungus usually doesn't spread through the glue. If it does a repair is only economical with very expensive lenses or if one simply wants to investigate how to re-cement a lens after cleaning. It is possible, but surely much more ambitious, than working with the complete groups.
And thirdly, collimation is less critical in older lenses with typically all spherical surfaces and fewer lenses. Modern lenses with sometimes several aspherical elements and loads of tiny corrector elements pose more of a problem.

I have taken apart, cleaned off fungus and reassembled successfully a few lenses and all were in perfect working order after the process. I cannot rule out, that I lost the last bit of collimation, but at least I could avoid serious and visible mistakes. It just needs time, care, a clutter free workspace and some application of common sense.

Ben
06-13-2012, 06:54 AM   #27
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Thanks all for your input! I'm a little wary about putting an unknown fungus in my mouth, so a 1:1 solution of ammonia and hydrogen peroxide sounds a lot safer

Ben, I have to agree with your findings. The Vivitar 70-210 worked fine after I disassembled and reassembled, as did the 28mm wide angle. That said, working "fine" isn't the same as brand new from the factory, but I can live with "fine" when we're talking about $20 lenses. There is no way in Hades that I would attempt this on my Canon L lenses or even an older expensive fast prime.

Thanks for the tip about the pencil marking! I'll definitely be using that one! I'm hoping the pancake lens isn't too complicated...I can't find ANY documentation about it on the web. In fact, I'm finding it hard to come across more than a couple of people even owning one...

Last edited by Judah; 06-13-2012 at 02:43 PM. Reason: Forgot a detail.
06-13-2012, 07:39 AM - 1 Like   #28
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Putting a lens element attacked by fungus in your mouth was a trick I learned from a former engineer of the famous Oude Delft optical factory in Holland!
I did it a few times and never felt sick, I only swallowed by accident an element once, but I could recover it a few days later and, be reassured, all fungus was gone, I just had to wash it...(*)

(*) I am NOT kidding, hauling a bucket around was not very funny!
06-13-2012, 09:38 AM   #29
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Philippe - I don't doubt you for a second! I have head of the saliva trick before, I'm just a little hesitant

What a story!
06-13-2012, 10:01 AM   #30
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saliva is the best start and least likely to damage the lens itself (and of course no-one said you have to suck on it saliva ia capable of leaving your mouth )
I here cold cream is a good non destructive as well.
and for stubborn the 50/50 IPA/Peroxide is pretty standard

I'm not certain this is fungus though, it does look like it could well be dried hardened lubricant. In any case if it is it's likely even cold cream or saliva may remove it..
If the elements have separated and you decide to proceed the stuff you need for regluing is Canada Balsam

they sell it here

1/4 POUND CHUNK OF CANADA BALSAM - Surplus Shed
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