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:

Dan W wrote:

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.

Yes, me too. I mean the sealings at least can prevent some dust particles to enter. I know the sealings will still allow air to enter for the lens to breath as it's zooming in and out, basics physics, but I'm expecting more from the multiple sealing in preventing dust particles to enter the barrel.

In my case, unfortunately the dust particle has fungus spores on it and I can see it grows around that dust on my lens as it sticks on the back of the front element.

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...

I gather all my silica gels I have and put it around my 70-200 while I look for compact dry cabinets.

How old are your silica gels? they dont last that long once they absorb all the water it can.

Yes Canon doesn't cover lens from fungus under warranty. That's too bad as it translates how the lens sealings integrity which is part of the lens manufacturing.

Again its not a "Air Tight seal" and never claimed to be. May I ask what part of the country do you live? I'm in Ohio, Ohio summers can be pretty brutal but we go most of the summer in the air-conditioning. Some days its humid and some its just hot and dry. I personally never had a fungus issue even though I have had condensation inside the lens after walking out to the air into hot 80%+ RH.

But its important to kill the fungus to stop it from growing and spreading to even other lenses on your bag. UV lights are cheap and maybe let it set in front of one for a few weeks when not in use with the caps off and shinning into the lens.

I understand your frustration though. I really wish you the best here. Please at least talk to canon about this, if its not too old (that lens hasn't been out too long) then they may still take care of you even if its not covered. Be nice and pleasant on the phone and see what they do for you. I've gotten upgraded for free to 1st class for nothing more then asking and being pleasant.

 Dan W's gear list:Dan W's gear list
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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