Inner fungal bloom issue, 6 month old Canon ef 70-300 L

meland wrote:

I've found that if moving from an air conditioned environment to the outside in very hot humid climates such as in Thailand, relatively cold cameras and lenses can almost instantly fog up with condensation and some of this can form on internal lens elements. Usually it dries out OK but presumably any residual moisture is a perfect breeding ground for fungal spores.

Try putting equipment into sealed plastic bags and allowing it to warm up to the ambient temperature before opening the bag, which largely resolves the condensation problem. This can take 15 minutes or more which is a bit of a pain but maybe that's preferable to suffering from condensation and fungal issues.

I concur with this statement and Steve's statements.

The issue is the humidity in the air, which no lens is "sealed" against (after all, the lenses are not vacuum packed). It's a totally different issue if you have a big drop of water, or a piece of dust that cannot penetrate the seal of a lens, versus a single water molecule suspended in air.

I had the same thing just happen not long ago, you come out of the air conditioned room, even if it's like 24 degrees Celsius, and go to the outside, into 30 degrees humid air, and you get condensation on your camera, especially the glass. If you operate your zoom lens under these conditions, humid air will enter the lens when you extend the lens (and the inside air volume has to increase), and can condense on the inside - bad. Even if the lens has warmed up, but if the outside air is very humid, eventually that humid air - if you zoom a lot - will end up in the lens, even though it will not condense. However, once you enter your air-conditioned room again, the temperature will be lower. As the lens cools down, the humid air now inside the lens will approach more and more the dew point, since colder air can hold less water vapor. So, that means in the worst case you could get some condensation again, but more likely, you just will have elevated humidity levels in your lens, again nice for mold. Eventually the air in the lens would of course equilibrate with that in the room, but anyway, that's the idea of the dry cabinets, to keep the lenses in dry conditions, get rid of humidity, water vapor.

Using a filter may have made things worse for the front lens, since you may have trapped most air in there. Put the filter on in dry conditions.