lens cases and fungus?

[msbarnes]

is it true?

I read that storing lenses in leather cases can cause fungus.

 

[maddoc]

Darkness, moderate temperatures and humidity are necessary to grow fungus spores. Additionally, leather is an ideal medium to grow fungus spores. So yes, under certain conditions your lenses stored inside leather lens cases will be infected by fungus.

 

[Leigh Youdale]

is it true?

I read that storing lenses in leather cases can cause fungus.

Not exactly true, but I'm being a bit pedantic. As an organic substance, leather is open to attack by fungal spores and other nasty microbes that can live and feed on the leather. A bit like bed bugs can live on the (unseen by you) skin particles that slough off your skin and remain in your bed.
Conditions of high humidity and warmth promote ideal conditions for such organic activity. It doesn't matter whether it's lens cases, camera cases or your leather shoes in the closet - they're all fair game and under the right conditions will allow fungus to breed and grow. The problem is when the fungus goes exploring and sometimes finds refuge inside lenses where it can still be moist and warm. Just not much to eat, but lens coatings seem to do almost as well.
So you can get fungus on and in lens cases without having a lens anywhere near them. It's not the lens that causes the fungus.
In many tropical countries where this is an ongoing problem (Say, Singapore for example) it's fairly common practice to have a false, perforated floor in the bottom of a closet with a low powered light globe operating under it to provide warmth, and a vent near the top of the cupboard to allow upwards air flow to take place. That changes the atmospheric conditions by drying and changing the air constantly, thus avoiding the problem. It's good for the clothes and shoes too as well as any camera gear.

 

[sevo]

Well, they will increase the fungus risk, as they regulate humidity towards the damp rather than dry side of things, as they block out all light, as dust from the case may add to the organic pollution of the surfaces, and as they are a hiding place for spores and cannot be sterilized.

But then, any storage in a soft container (camera bags included) is not advisable in humid conditions.