Is this a fungus spot on the rear element of this EF 24-70 2.8

Hi,

it looks fungus to me, but before you start with the fungus paranoia, some facts:

- There are about a million fungus spores per cubic meter. Don't waste your time trying to kill them, just do not create the environment to allow them to form a colony.

- Spores are extremely resistant, so even if you try to kill them, probably it won't work.

- The spores need two things to form a colony, food and water. Food is (inside the lenses) normally any fat residue. The coating is not food. Water is taken from the air.

So, I would have the lens cleaned.If no-one wants to clean it, you could do it yourself with an alcohol based cleaner (like the zeiss disposable cleaning wipes). There might be a residue that cannot be removed, and in some cases, there might be some damage to the coatings. After you clean it, it won't spread until the conditions to form a colony are back.

So, keep your lenses in a dry environment. And don't worry about putting this lens with the others, or waste your time trying to disinfect everything. The colonies can grow, but they cannot fly or jump from one lens to the other. Only the spores fly,and again, they need a proper environment to form a colony.

And btw, the spot in your lens is very small, I really doubt it will have any impact in your images, but clean it anyway, otherwise the colony can grow much bigger.

If there is anything not clear, please tell me. I'm not a native English speaker.

Cheers!