Have you ever stepped out of your hotel on to the streets of a humid destination, lifted your camera up to take photos of the activity on the street and been met by a cloudy, foggy lens? You rapidly try to wipe the fog off the lens, but to no avail, it returns almost instantly. So much for that shot of the monks walking down the street … all I see now is their backs about a block away. This happened to me several times in Myanmar this summer.
Although there is no instant fix once your lens has fogged, there are things you can do preventatively!
Keep your gear at a study temperature. This is very difficult when you are going from hot and humid weather to the beautiful air conditioning in the hotel. But, remember your camera doesn’t have feelings. It doesn’t need to cool off like we do!
Keep your backpack / camera gear stored in the shade when possible when you are outside.
Carry an umbrella to keep the hot sun off both you and your camera gear.
Try to minimize how often you go from the hot sun to air conditioned locations.
Try to keep the air conditioning to temperate, not as cold as you want to be after 40 degree heat.
Keep your camera gear in a bag or backpack, possibly in a closet out of the direct stream of cold air
Keep your camera gear in the bathroom if it is not too damp, with the door closed to keep the air conditioning out (I did this a lot in South East Asia)
Give your gear time to acclimatize. If you cannot avoid going from cool air conditioning to blazing hot sun, make sure you plan sufficient time for your camera to adjust to the new temperature. When you leave the cold air your lens (and mirror inside the camera) will almost automatically fog, just like your spectacles do! Because there is so much glass in a lens and they can be very thick, it takes time for all of the layers of glass to warm up and the fog to go away. If you want to be able to shoot clearly at 8:30am, you should consider warming your gear up half an hour to an hour prior.
Pack silica gels or other absorbent materials. Keep your silica gel packs from that new leather jacket, your new shoes or any other products that might be prone to moisture. Stick the little packs in around your camera gear to help absorb moisture whenever you are in a humid climate.