Before you avoid taking your camera outside this fall, let me be clear: it takes a pretty substantial temperature change to produce the kind of condensation that can make it hard to take pictures or, even worse, damage your gear. It’s the kind of thing that most often happens when it’s really hot outside, or really cold.
In warm weather, condensation usually appears at the most unfortunate time—right when you want to start shooting. When you take your camera from the relatively cool and dry confines of an air-conditioned house or car, if it’s a particularly hot and humid day when you get outside you may look through the viewfinder only to see a cloudy fog. That’s condensation on the lens and viewfinder, and potentially in them as well. It takes several minutes of acclimating to the outside temperature before you can shoot.
In cold weather, the reverse is true: when you take your camera outdoors in the dry, cold air, then bring it back inside to a warm house, condensation will form all over the camera and lens.
The solution to each moisture problem is time. Before going outside in the heat, make sure your camera is stowed in its zipped up camera bag. Allow the bag to stay outside and slowly come up to the temperature of the ambient air. This may be as quick as 15 minutes or as long as a few hours, depending both on the size of the gear and the nature of the bag. If you’re in a hurry, before you set out, put your camera and lens into a sealed plastic bag, which will allow the gear inside to acclimatize quicker.
Before bringing cold cameras and lenses indoors on a freezing day, again seal them up in a bag. The camera bag should do fine, but for absolute protection against humidity, try a sealed plastic bag. Condensation may still form, but this time, it will be on the outside of the bag, rather than directly on the camera equipment.
In each case, you can also add the extra step of not moving straight from one extreme to another, but stopping at someplace in between. A garage or basement, for instance, may represent a happy medium between indoors and out; not as cold in the summer as indoors, but not as warm in the winter, either. Allowing the camera to change temperatures gradually can help ease the worry of condensation.
What do you do if you forget these steps and do find condensation on your gear? First, don’t try to scrub it off the lens or filter. You’ll only increase the odds of creating smears and scratching the coating, and you might even help work some of the moisture inside the lens. Also, do not remove the filter from the lens, or the lens from the camera body. Both will risk getting more condensation on sensitive internal elements of the body and the lens.
If you’re seriously concerned about the amount of moisture in or on your gear, try the old cell phone trick: place the gear in a sealed plastic bag with dry uncooked rice or, better still, a super-absorbent silica packet (the kind that often come boxed with electronics) that will grab as much moisture as possible.