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12-18-2020, 04:01 PM   #1
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Cleaning the lens of something

Hello everybody. First of all, I am sorry to disturb you with my question, since I am sure it is not the very new topic. Though in my specific case, the more I look and read, the more confused I get.

I have ordered myself a Pentax M 40mm f 2.8. I got it quite cheap, but it has some kind of a problem, because it was not used for ~30 years. It has some sort of haze/fog/fungus or something else inside on the rear lens. Please help me identify my problem (see the picture - at this time, this is the only photo I got) and let me know if I could clean it up. If it is manageable to repair this with easily accessible and not too expensive materials, and without damaging the glass, the coating, etc.?

I have read about these sorts of problems, but this is the first time I face it myself, so I would appreciate your advices. Thanks!

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12-18-2020, 04:27 PM   #2
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It is difficult to tell from the photo if the haze is on the inside or outside. If it is on the outside it should clean off with a bit of lens cleaning solution (for photo equipment), a touch of hydrogen peroxide (if fungus) and a clean lens cleaning cloth.

If it is on the inside on the rear element only it may be able to be clean without much disassembly. If you have the proper tools and skills you may be able to DIY. If consider professional cleaning or returning the lens for refund or asking for a partial refund.

Check the disassembly database or for DIY videos on youtube. Prime lenses in the M series pretty much share the same basic designs so you may not need an exact match on the model.

Pentax Lens Disassembly Database - PentaxForums.com
12-18-2020, 04:48 PM   #3
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QuoteOriginally posted by Kiparisas Quote
so I would appreciate your advices.
If it is just the rear element, then removing it is easy ....with the right tool. You need a spanning wrench. You place it in the two notches at the 10 and 4 o'clock position in your picture and turn anti clockwise......remember which way round the glass element comes out !


Pro spanner wrench for camera lens repair opening open tool stainless steel -MFS | eBay
12-18-2020, 06:26 PM   #4
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I just bought a Pentax M 50mm f:2 at a thrift shop that looks about the same, something on inside of rear element. I am going to take it apart and try and clean it myself. If I mess it up I'm only out $3.

12-19-2020, 07:09 AM   #5
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So long as the fungus hasnt etched the glass it should clean off with some peroxide. You may need to disassemble the rear element to get at it.
01-15-2021, 02:43 PM   #6
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Hello guys, thank you very much for your help. I have just received my lens and ordered the spanner wrench. I are however, that the fungus is present on the front lens as well. But there is no place for spanner wrench in the front. How can I remove the element in the front? Thank you once again, I'll let you know how it goes

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01-15-2021, 04:09 PM   #7
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QuoteOriginally posted by Kiparisas Quote
How can I remove the element in the front?
The plastic ring with the writing on it will unscrew anti-clockwise. They can be tough to shift. my method is to use double sided sticky pads, about six of them. Then a lens mount cap can be used to get traction. You can then see how to get the front element assembly out.

Have a look here to give you an idea of how
01-15-2021, 04:15 PM   #8
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Sometimes it's difficult to diagnose the exact nature of the problem until you take the lens apart.

Recently I purchased an 1960's vintage Pentax lens. After receiving and inspecting it, it looked like it had a form of haze on one of the elements. After taking the lens apart, I determined that this defect was located "between" two cemented optical elements. Obviously, what I thought was a simple case of haze turned out to be a case of "lens separation" (which is virtually always an incorrectable terminal condition)

02-12-2021, 03:35 PM   #9
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Dear everybody! Thank you very much for your help - after struggling for a while with removing the name ring I have successfully cleaned fungus using the solution of peroxide and amonia. The lens is free of this problem. The fungus was on both rear and front element, so I took everything apart and managed to put everything together back in order! I am very happy about my experiment and it is this forum that I have to thank for this.

Though now there is another problem I cannot solve - I am not able to clean it well for it to be transparent. There are always some small particles of dust (see the pictures), and I am almost giving up on this task, because I cannot control them. It is dust for sure, not something else, since they move. Though I cannot clean it completely, because the new ones always emerge from the cloth fibres that I clean it with. For now I have tried antibacterial lens cleaning wet wipes, several new and sealed microfiber wipes, all of this accompanied by a good air blower and a baloon of compressed air. I have also tried using a new lenspen, though it always creates more smudges than there were in the first place. I even tried the dslr sensor cleaning brush (quite expensive option, but seemed to be working for a while - maybe there is some charge that attracts the particles or something similar).

Any ideas how to get rid of this small dust? The air blower blows away only the bigger particles, but these small ones seem to be adhered to the glass more firmly and since they are small, I can only move them to some extent, but not remove completely. Looks like they have a static charge to the glass. Would you have any advice for solving this problem? I am a bit out of options and would appreciate any help. Thank you once again!
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Last edited by Kiparisas; 02-12-2021 at 04:03 PM.
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