The first time we noticed the problem, we were on a shoot in Puerto Rico. As the doors to our air-conditioned hotel opened, we pulled our camera from the bag and looked through the viewfinder only to see steamy Old San Juan blurred out in a thick haze.

No, a fog had not descended on this Caribbean town, just on the front of our lens. We wiped it clean with a lens cloth, took a few test photos and then hopped in an air-conditioned van and headed off to the assignment. When we got out of the van, sure enough, the lens was fogged again.

It's times like those we really wished we had some Defog It. Never heard of Defog It? We actually hadn't heard of it either until recently. As its name suggests, Defog It is designed to keep your lenses from fogging up.

The anti-fogging solution, made by Nanofilm, is available in moist towelettes or in liquid form which you gently wipe on the front of your lens—or eyewear—–to prevent it from fogging while moving between temperature-changing environments.

One wipe/squirt of Defog It should keep the fog off your lens for a whole day though the company has put it through more rigorous testing. In one test, a Defog It-treated lens was held over hot steam for an hour without fogging up. In another, coated lenses were moved between hot and cold environments 100 times without fogging. If we can get it to work in New York City in soupy August weather, we'll be satisfied. According to Nanofilm, Defog It has been proven safe and effective on optical lenses, eyeglasses, safety goggles. But to be on the safe side, test it on one of your less expensive lenses first before you try it on your L-series glass.

Cost: $7.49 for three reusable anti-fog cloths in a plastic carrying case; $5.99 for kit with 5ml bottle of anti-fog liquid and microfiber cloth.

Further information: www.defogitworks.com