Designed for time-lapse and outdoor shooters, at night, in cold weather, and humid locations
If you've shot time-lapses or long exposure photos at night, or if you've been out in cold, wet or humid environments with your camera, you've probably had a fogged up lens or two. Having to wipe the lens can be an inconvenience for photographers shooting stills, or totally impossible for those who are creating movies.
It can also lead to damage, or a persistent condensation problem if the fog gets inside the lens. I won't get too technical here, but the reason the condensation forms on your lens is because warm air can hold water vapour better than cold air. And when the comparatively warm air hits the cold metal and glass on your camera, it gets colder, dumps the water, and ruins your shoot. The temperature where the nice water vapour in the air turns to bad condensation on your lens is called the Dew Point.
If you can keep your lens warmer than the dew point, you won't get condensation on or in your lens.
In the past I've used chemical hand-warmers to my heat lenses, but they're unreliable, bulky, you can't tell when they've stopped working (until you get home and see the photos), and when you replace them (every hour or so) it's easy to knock the focus ring, nudge the zoom ring, move the camera on the tripod, or even set yourself on fire.
All of these things have happened to me, one time all four at once, but hey, I was drunk, and that's a story for another day.
With The Monkey Claw, you can have a small, lightweight electrical heater than can attach securely to any lens in seconds, and run up to 7 hours on an AA battery pack.
For those of you who shoot handheld, out in the cold or at night, The Monkey Claw also helps keep your fingers toasty.