Fungus (?) inside RF 70-200 F4 L

Started 3 months ago | Discussions thread
Dan W Contributing Member • Posts: 834
Re: Fungus (?) inside RF 70-200 F4 L

Sinawang wrote:

MannyV wrote:

Ever move from aircon room to outside in a hot humid country? Ever noticed what happens to lens when you do that? Those who live in such environment know how this condensation occurs. Both inside and outside of lens and irrespective of weather sealed or not. Google how to avoid this in future. Also dry cabinets are a hot commodity in such places.

The spot stays there after 24hr since I found it on the lens, it's not like condensation. I know about condensation, when the temps on both side inside & outside is equal, the fog will gone, but this one doesn't.

I check it from time to time to see if it spreads further radially, hopefully it won't grow any further.

Not something new with lens. Any expensive stuff that can corrode, video tapes, etc would be tried and stored in those cabinets when not in use. Wish you luck.

I dont know of any lens that is air tight and sealed that way. "Sealed" L lenses just means its seals out dust and a little rain, not dropped in a pond sealed. If you look at any doubled glazed windows sash over 20 years old, you will likely see the same thing in your lens, a fog that never goes away. Thats because the air tight seal has broken down over the years and is letting moisture in.

In the case of lenses, just humid climates and humid storage can cause this. Unfortunately this is not uncommon in some areas. Condensation may happen when you come out of a well air-conditioned home to a humid outdoors. But thats not what "HAS TOO" happen to get fungus and mold. I fight mold on the north side of my house because it never sees direct sunlight. Look on eBay and you will see modern day lenses as well as legacy lenses that will state in the listing that their lens is "Fungus Free". First thing I look for or ask when considering a second hand lens.

The good news is you can have it cleaned, bad news is it won't go away on its own. You need to make sure you dry out the lens very well in a dry cabinet or leave it out in the sun on hot dry days to kill off the fungus. at least that will stop it from growing worse. UV will kill fungus.

You may be right about not covered in the warranty, its not really a manufacturing defect. It's more an environmental issue that is out of Canon's control. But I would still make that call to canon and see what they say. won't cost you anything to call other then your time... Good luck...

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Canon EOS R Canon EOS R5 Canon RF 50mm F1.2L USM Canon RF 35mm F1.8 IS STM Macro Canon RF 24-105mm F4L IS USM +1 more
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