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04-18-2017, 08:09 AM   #1
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Pentacon 135MM F2.8 Bokeh Monster M42 Mount

Hey everyone,

Looking to get some advice from you intelligent lot! I recently purchased a Pentacon 135mm F2.8 and although the cosmetic condition is very good, there are some issues with the internal glass elements. I will attach some images for you to view and hopefully you could tell me if this lens is a bum or not.

It seems like the front and rear elements, on the interior side, have some wiping marks and are quite easy to distinguish. Then on one of the middle glass elements, the edges seem to be cracked or the adhesive has cracked and formed some yellowish crusty stuff.

What are your opinions on the lens? Keep or return? I generally keep all my gear well looked after, so I am annoyed that there was no mention of this on the listing.

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04-18-2017, 08:58 AM   #2
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How's the IQ? The rear wiping marks look like dirt to me, does it wipe off?
04-18-2017, 09:09 AM   #3
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The blemishes look external. Try to clean them of and then look again. The yellow stuff is glue which has cracked over the years. Nothing to worry about I'd say.
04-18-2017, 09:54 AM   #4
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Depends on how much you paid for it, and how it was described to you. A nice copy of this lens can take some beautiful pictures and they are fairly easy to service. The glue I wouldn't worry about, the cleaning marks are fairly typical for these lenses but it might clean off, too. So if you can do thisbyourself, returning the lens might actually be more hassle.

04-18-2017, 10:01 AM   #5
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Does look a little rough - what are the results like ?
04-18-2017, 01:58 PM   #6
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To wipe off the dirt I would have to disassemble the lens, so not sure if I want to go forward with that. And I would test it, but I only shoot film and don't really want to waste a roll for it. But the seller is happy to refund it.

Would anyone have images of how to disassemble the lens? I might go for it, if I can follow some sort of guide.

Thanks for the replies folks!
04-19-2017, 12:30 PM   #7
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QuoteOriginally posted by dcshooter Quote
The yellowing is minor balsam separation along the edges of the cemented group in the front. See this diagram:

It's a $100+ repair, but if it is merely confined to the edges, it shouldn't really affect your pictures in any way.

To clean the rear element, all you have to do is get a lens spanner and turn the inner retaining ring notches until the ring and element come out.
Cheers for the comment. I have cleaned the front and rear elements and it is now much cleaner! But I think someone had previously opened it up and left the cleaning marks. Referring to your diagram, do all Pentacon 135mm F2.8 have the same optical formula? Just to let you know, mine is the preset version.
04-19-2017, 02:52 PM   #8
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Marks directly on the lens are rarely ever observable in the image for the simple fact that the focal point of the lens is NOT there.

Even saw an interesting experiment online once where they kept putting more marks/dust etc on to a lens to see at what point it become obvious in the photo image. It took a while!

Apparently clean lens surfaces are greatly overrated


Last edited by Theov39; 04-20-2017 at 02:06 AM.
04-20-2017, 04:14 AM   #9
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QuoteOriginally posted by Theov39 Quote
Marks directly on the lens are rarely ever observable in the image for the simple fact that the focal point of the lens is NOT there.

Even saw an interesting experiment online once where they kept putting more marks/dust etc on to a lens to see at what point it become obvious in the photo image. It took a while!

Apparently clean lens surfaces are greatly overrated
Thanks for that. I did remove a lot of the grime of the elements, but not everything. It should perform much better. I just need to test it now!
04-20-2017, 06:31 AM - 1 Like   #10
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When using a long enough extension ring, you can also get the front element dust particles in focus
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