Fungus on mirror: preventing spread to clean lenses

Krzys · Jul 21, 2009

I have a clean 80mm f1.9 on the way for my Mamiya 645. The only concern is that when I purchased the body a week ago there was some small fungus growth on the mirror. I gently cleaned what I could see off and probably added some scratches in the process (In my opinion a fair trade off). I am going to leave the body in the sun for two days then store my equipment in a dry box with silica gel packs.

Are there any more preventions I can take to make sure my new lens stays fungus free?

rternbach · Jul 21, 2009

I have a similar situation with a lens I bought knowing it had a small amount of fungus on it. I took it apart, cleaned it gently with lens cleaner--which had a small amount of isoproyl and vinegar added. I put the lens inside a baggie with dessicant and also put it in the sun for an afternoon. I keep it in its own baggie with its own dessicant inside a plastic container so it will stay dry and not contaminate any other equipment. I plan on checking it every so often, between times when I'm actually using it, to see if the fungus is coming back. I guess this is similar to what you have done except for the alcohol+vinegar. My understanding is that fungal spores are everywhere but fungus needs moisture to grow so keeping things dry and in a low-humidity environment will prevent its growth.

Krzys · Jul 21, 2009

How long must the fungus sit in the sun for it to die off? Is there any information on this?

WolfTales · Jul 21, 2009

I would be more concerned having the foam rubbers, rubber gaskets, and lubricants deteriorate if you were to leave the entire body in the sun. UV rays tend to deteriorate things etc...

rternbach · Jul 21, 2009

I haven't seen any good info on this (i.e. how long to leave it in the sun or in UV). In fact, there are those who say UV and sunlight don't help at all. Seeing that your mirror is the problem surface I would rely on flooding it with alcohol and vinegar (use a Q-Tip to apply the sol'n) and very gently drying it with lens tissue (or just drain the sol'n into the tip of the tissue). Protect the area around the mirror with lint-free tissue or lens cloth while washing. I know there are those who will say this kind of sol'n is too strong for lens coatings and mirrors but I think it is worth the risk. In my situation the fungus was in the periphery not the center and it had not etched the lens. In your case you could always replace the mirror if all else fails.

Sirius Glass · Jul 21, 2009

I suppose that you could send it to Mamiya to replace the mirror and have a CLA done for fungus.

Steve

la.triglia · Jul 21, 2009

I am sorry but I think that your problem is more frequent than we think.

http://www.chem.helsinki.fi/~toomas/photo/fungus/

mikebarger · Jul 21, 2009

Since it is a mirror, I think I'd try a dilute mixture of Clorox 1:25...use a cotton swab or q-tip.

Mike

Sirius Glass · Jul 21, 2009

Be careful, it is probably a first surface mirror.

Steve

rternbach · Jul 21, 2009

mikebarger said:
Since it is a mirror, I think I'd try a dilute mixture of Clorox 1:25...use a cotton swab or q-tip.

Mike

Makes sense to me.

Fungus on mirror: preventing spread to clean lenses

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