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Is this fungus? (on Pentacon 135/2.8)
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PostPosted: Thu Feb 21, 2013 10:36 am    Post subject: Is this fungus? (on Pentacon 135/2.8) Reply with quote
I bought a Pentacon 135/2.8 zebra in exakta mount with two extension pieces.
The focus is quite stiff so I want to relube the objective soon, but I still need to buy the replacement mount to M42 to get it fully functioning.

I could also buy a Exakta - EOS adapter. Do people have good experiences with that?


Upon examining the lens I spotted some imperfections on the rear glass element.
Can someone tell me if it's fungus?





PostPosted: Thu Feb 21, 2013 10:42 am    Post subject: Reply with quote
It's typical Meyer / Pentacon coating degradation. Leave it as it is since it will peel off if trying to clean it. It has minimal affect on lens IQ despite the infectious look.


PostPosted: Thu Feb 21, 2013 11:07 am    Post subject: Reply with quote
Pancolart wrote:
It's typical Meyer / Pentacon coating degradation. Leave it as it is since it will peel off if trying to clean it. It has minimal affect on lens IQ despite the infectious look.

+1 not fungus.


PostPosted: Thu Feb 21, 2013 11:56 am    Post subject: Reply with quote
@administrator, sorry for posting in the wrong subforum and thanks for moving it!

Thanks for the response Pancolart and Attila, it's comforting to known the glass is ok.
Now I only need to service the objective.

Any thought on Exacta-EOS adapter vs fitting a M42 adapter mount?


PostPosted: Thu Feb 21, 2013 12:08 pm    Post subject: Reply with quote
chris_zeel wrote:
@administrator, sorry for posting in the wrong subforum and thanks for moving it!

Thanks for the response Pancolart and Attila, it's comforting to known the glass is ok.
Now I only need to service the objective.

Any thought on Exacta-EOS adapter vs fitting a M42 adapter mount?


Exakta/EOS adapters are cheap and easy. The one from Ebay seller Big-is should reach infnity.

The exception is Exakta auto lenses with the big knob on the side, many of them won't fit on the adapter.


PostPosted: Thu Feb 21, 2013 2:27 pm    Post subject: Re: Is this fungus? (on Pentacon 135/2.8) Reply with quote
chris_zeel wrote:
The focus is quite stiff

I think this answers your question. I've had several lenses like this with stiff focussing, and on every one the grease on the focussing threads had separated into a thin oily liquid and a heavy sticky grease. This is caused by excessive heat - perhaps the lens was left on a sunny window cill or in a car. The lighter oil evaporates and recondenses on the inner surface of the glass. which causes this spotty effect. It's more than likely you'll find there is an oily deposit on the diaphragm blades too. Fortunately it's easy to clean off once the lens is dismantled.


PostPosted: Thu Feb 21, 2013 5:10 pm    Post subject: Re: Is this fungus? (on Pentacon 135/2.8) Reply with quote
peterqd wrote:
chris_zeel wrote:
The focus is quite stiff

I think this answers your question. I've had several lenses like this with stiff focussing, and on every one the grease on the focussing threads had separated into a thin oily liquid and a heavy sticky grease. This is caused by excessive heat - perhaps the lens was left on a sunny window cill or in a car. The lighter oil evaporates and recondenses on the inner surface of the glass. which causes this spotty effect. It's more than likely you'll find there is an oily deposit on the diaphragm blades too. Fortunately it's easy to clean off once the lens is dismantled.



Sounds very comprehendible. The diaphragm leaves do look like they have that oily deposit on them

Would you clean if off the lenses? Or leave it as is?
I haven't been able to test the lens yet so I don't know how the image quality is.


PostPosted: Thu Feb 21, 2013 5:36 pm    Post subject: Reply with quote
Me personally, I would clean the lens if it is indeed oily deposits and not coating degradation. But I have the right tools and I've refurbished lenses before. The older primes are usually fairly easy to work on, so I wouldn't be overly concerned about it.


PostPosted: Thu Feb 21, 2013 7:15 pm    Post subject: Reply with quote
Judging by your first pic I would say this definitely needs to be cleaned. It's not difficult at all to remove the rear element,
just make sure you replace it the right way round.

Excellent instructions for the Pentacon 135/2.8 on this link
http://www.mqcvisions.net/Pentacon_135_2_8/Pentacon_1.html


PostPosted: Thu Feb 21, 2013 9:58 pm    Post subject: Reply with quote
peterqd wrote:
Judging by your first pic I would say this definitely needs to be cleaned. It's not difficult at all to remove the rear element,
just make sure you replace it the right way round.

Excellent instructions for the Pentacon 135/2.8 on this link
http://www.mqcvisions.net/Pentacon_135_2_8/Pentacon_1.html


Is this guide also applicable for the preset zebra? Is it constructed in the same way?


The rear element can indeed be easily unscrewed.
How do I best clean the glass elements?


PostPosted: Thu Feb 21, 2013 11:36 pm    Post subject: Reply with quote
I prefer disposable wet cleaning tissue for eye-glasses. Cheap, does not leave residue, no need to clean it.


PostPosted: Fri Feb 22, 2013 12:51 am    Post subject: Reply with quote
chris_zeel wrote:
Is this guide also applicable for the preset zebra? Is it constructed in the same way?

The guide is for a later version but still preset. As far as I know only the cosmetics were changed.

Quote:
The rear element can indeed be easily unscrewed.
How do I best clean the glass elements?

I just use washing-up liquid, warm water and a tissue. Be gentle because the coatings could be easily damaged on this older
lens.


PostPosted: Sun Feb 24, 2013 9:51 pm    Post subject: Reply with quote
Thanks for the advice people!

If I would be opening the glass element for cleaning, is the orientation critical when putting them back together?
I don't means back to front orientation of the lenses, but the rotational orientation.


PostPosted: Mon Feb 25, 2013 10:34 pm    Post subject: Reply with quote
Anyone?

Or am I being stupid..?


PostPosted: Mon Feb 25, 2013 10:40 pm    Post subject: Reply with quote
I never worry about rotational orientation when I put a lens back together. Some folks say a lens must be colimated after disassembly and reassembly, but I wonder about that. I've taken apart and put back together a lot of lenses, and all of them were constructed so that the glass elements could sit in the tubes in one way only, and it's always a precise fit; no wiggle room. It simply wasn't possible to mis-align an element unless one was being incredibly fumble-fingered. So, no, I wouldn't worry about it.
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