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Message |
    
Ezio
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 10, 2004 - 02:13 pm: | 
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I have just got a Miranda 135mm tele in absolutely immaculate conditions, but with what seems to be a totally unknown (to me) type of fungus. The lens themselves are not affected, but the whole of the internal barrel behind the front lens is covered with countless small white dots which look exactly like a fungus growth on a petri dish. Has anyone ever encountered this? In any case, how do I proceed to remove the front lens and clean this mess? |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 10, 2004 - 02:22 pm: |
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Sometimes aluminium gets some kind of 'pocks' when stored in a humid environment for a long time. Many lens barrels are made from aluminium. The only way to remove this corrosion is to sand and to repaint the surface. |
rick oleson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 10, 2004 - 05:48 pm: |
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Yes, these are aluminum oxide - aluminum's version of rust. it can get pretty bad if bare aluminum is stored in the damp, but it isn't fungus and it's basically a cosmetic issue if it isn't on moving parts. |
Ezio
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 11, 2004 - 01:31 am: |
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Thank you both - vey interesting. The seller says that the lens spent the whole of its life at Lake Tahoe, i.e. in a very dry/high altitude climate that would seem the least conductive of this type of corrosion. Also, Rick: why "a cosmetic issue"? You mean that there is no internal reflection from these white spots? |
rick oleson
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 11, 2004 - 06:39 am: |
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Hi Ezio:
I suppose they could if they get that bad, depending on where they're located. What I was thinking of is that they do not threaten your glass like fungus would. I'm not familiar with the construction of that particular lens, but in most cases to get into the barrel you would unscrew the front ID ring (does it have spanner slots in it?) and then you can probably unscrew the front cell of the lens, exposing the interior of the barrel from the diaphragm forward. The diaphragm itself may then be removable; in some lenses this comes out as a neat modular subassembly, in others it's a handful of nasty loose parts once you unfasten it. The rear cell and remaining diaphragm linkage usually are removed from the rear.
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