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05-04-2014, 07:12 PM   #1
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Salvageable fungus?

I received a Pentax M 50mm f1.4 from my father, but it has some fungus on the inside rear elements that greatly reduces contrast. Is this even fungus or is it to due with coatings? And is it possible for it to be cleaned?


Last edited by cgchang; 12-31-2015 at 12:15 PM.
05-04-2014, 07:33 PM   #2
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Looks like fungus. It will probably cost a bit to clean and the results will be variable (see below).

While the fungus can be cleaned the damage to the coatings may be substantial. If so then cleaning will improve contrast but will not improve any 'loss' arising from damage to coatings.

If you have a couple of dollars I think it is worth the effort of buying a lens opener/ caliper thingy (funny little gadget found on fleabay) and opening up the lens - do it yourself clean job. If it doesn't work out at least you can keep the gear you bought and use for a less terminal lens. Also you may find salvageable parts of the lens useful for fixing another .......

Last but not least a deglassed lens may be useful should you consider a reversed lens macro set up. The deglassed lens can attach to the camera act as a tube with aperture. The reversed lens would be coupled with the filter thread via a male - male connector

Anyway - don't throw away it can be useful one way or another.

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05-04-2014, 07:42 PM   #3
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Yikes! I'm going to have trouble sleeping tonight, after looking at the coating of fungus! It looks like a petri dish. Seriously, that image is giving me goosebumps.
05-04-2014, 07:49 PM   #4
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It's not as bad when looking at it with the naked eye, just the angle of the light shows it all.

05-04-2014, 08:05 PM   #5
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Sorry to say it is pretty bad and the petri dish comparison is a good one. I'm not sure if I have seen worse to be honest
05-04-2014, 11:04 PM   #6
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Yeah that is pretty bad and I`ve seen a lot of fungus in lenses. Gotta be way up on the list as worst case of fungus. Possible to clean, depends on how long it was growing and if it etched the coating.
05-09-2014, 01:29 AM   #7
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Strip the lens and clean the elements it doesn't matter in the slightest. Don't worry about damage to the coating,


Photographers managed for 120 years without coatings, I know the lenses were simpler, but were talking only one or 2 affected surfaces here.


I use almost exclusively 70 year old glass with little or no coatings, and its no problem. It used to be a problem in film days because the image was seriously degraded without coatings and there was no recovering it. In digital images you simply slide the contrast up several notches hey presto dial in coatings.


I get images from an uncoated 135 that are indistinguishable from a coated takumar 135 simply by increasing the contrast in post.


You will have to discover how to get to the element, either entirely from the front or from the rear. I had one lens that removal of the front decorative ring allowed all elements to slip out, on two others, the rear set unscrewed entirely from the rear.


Beware of complex lenses that when you attack the parts and disassemble, small bits fall out, like aperture detent balls.


The biggest issue is reassembling the lens correctly and packing the elements tightly. I had to strip a seriously low contrast and poorly resolving lens that the last owner hadn't reassembled properly. After reassembly and whacking/packing the elements the lens was a decent performer. Tiny misalignments lead to major aberrations.
05-09-2014, 02:33 AM   #8
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QuoteOriginally posted by Imageman Quote
Strip the lens and clean the elements it doesn't matter in the slightest. Don't worry about damage to the coating,
On that lens the back element should come out easily. Just get or improvise the right tool to unscrew the retaining ring. The beauty of the M primes is that they are simple to disassemble. Smear some cold cream on the offending vegetation and leave it for a while - it should then come off. The coating will probably be OK - SMC is remarkably resilient. Just make sure that you put the element back the right way round when you re-assemble.

05-09-2014, 01:03 PM   #9
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Well I attempted to disassemble the lens to try and clean it. Looks like the affect glass is just behind the aperture blades but the the side facing the rear of the lens. Couldn't figure out how to get to it so I called it quits to be safe and reassembled. Ended up breaking the tip of my mini screwdriver tightening the small screws On the plus side I cleaned a speck of mold from another lens.
05-09-2014, 02:41 PM   #10
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Is this any help ?
05-09-2014, 04:02 PM   #11
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I didn't see in the video if he's able to access the glass on the other side of the aperture blades. It would have been after about the 5min mark where he pops out the lens. My fungus affected glass is under that piece.
05-09-2014, 05:26 PM   #12
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How about this guide ?
05-10-2014, 07:08 PM   #13
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Still couldn't figure how to get at the lens. May have to remove the lens mount, but unfortunately the screws are very tight which is causing screw bits to wear out the head of the screw or the tip breaks. So I may just call it for attempting to self fix. Thanks.
05-10-2014, 07:21 PM   #14
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Are you using a JIS driver to remove the screws? I have yet to have one slip and strip the head on me, even on screws that I have been unable to move.
05-10-2014, 07:29 PM   #15
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No been using a phillips #000/#00. Haven't come across a JIS around here.
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