To add on. If it really bothers you, or the difference in temperature is really big... like between -20 and 20 deg, you might want to bring along some ziploc bags. Before entering a warm environment from a cold one, place your camera with lens in a ziploc bag and seal it. Bring it into the room, and you will see the condensation form on the outside of the bag, and not on the camera inside the bag. After the temperature of the camera stabilizes, (maybe 10 mins?), you can take it out of the ziploc bag. And yes, you can keep the ziploc bag and use it over and over and over again.