I've had a bunch L-Series Canon Lenses here for many years and no problem with mold. The A/C keeps the humidity down in the house.
What is a problem is in the summertime when you take your lens outside and the humid air hits them. The lens is relatively cold from being in the A/C in the house so they fog up. It can take a half-hour or more before they really clear up. The trick is to put the lens, in its case or Pelican, in the garage or car for an hour or so, so that its temperature can catch up to the outdoor temperature.
|