As mentioned, this problem arises when you take your camera from a cool, air conditioned interior to a warm, humid outside. In extreme cases, you can also fog up the interior elements, so no, anti-fog won't help. The reason Binoculars don't fog up internally is because they are purged with nitrogen to prevent this. My solution to this problem is a hair dryer. Before going outside to the warm, humid atmosphere, I'll take a hair dryer on low to medium heat, and wave the warm air over the lens and camera until the chill is removed. Some extremes in air temps and humidity will require more warming, but this eliminates the problem of fogging, and I highly recommend it. And if you're wondering, you will not fog the lens up inside with the hair dryer, because you're using a dry heat. It's the temp change, coupled with increased humidity outside that causes the heavy fogging.