I've done a lot of work in cold weather. Not with digital, though. I imagine, besides batteries, the needs are the same. When I ran around with my SLR, I usually kept to the small zoom lens (to avoid changing too often) 35-105, I believe. With care, changing lenses shouldn't be a problem. Running outside your house for 15 minutes shouldn't be a problem much either. But if you're going to be gone a while, I'd suggest a floppy coat to pull over the camera. It's going to get cold anyway if you are out several hours (depending on how long the camera is poised outside to the elements). The main things to remember are: Take a ziplock baggie (I used 2 in my days) or baggies if you are taking extra lenses. Before going back inside, place all camera lenses and body into the baggie. (I usually put THAT baggie into another one). Any condensation will form on the baggie(s)...not on the mirror, lenses, or between the lens elements (the worst). Also, the film should go in a baggie or snapped tightly in the plastic film cannister (if there was one). For film cameras, let the extra film get cold. Just keep it in the camera bag. It can fog, too. Especially in wet winter places like Germany. Be careful when changing film or lenses not to breath on any of it...just keep your distance. (from your mouth...hehe) Just as you would avoid pointing a "filmed" camera directly at the sun with the lens cap off, watch for glare from sunny snow. Since SLR cameras use mechanics, be careful of extremely low temperatures. Not directly related to the cold, but if you are shooting lots of snow, be aware of the exposure problems. Bracket your shots. Remember, ALL cameras look at an exposure as a zone five gray. Snow is more likely zone seven or eight, depending on shadows and overcast.