We all know that temperature extremes play havoc with technology, and cameras (having both optics and electronics) seems particularly sensitive. I live in the northern Great Lakes region of the USA, which is subject to fairly harsh winters - last winter we had sustained temperatures as low as -20F. More importantly, going from outdoors into a heated building produces up to 90F degrees of temperature variation in just minutes... My Nikon Coolpix 4300 point-and-shoot has survived outdoor shooting sessions in this weather; usually I would shoot, turn off the camera, bring it in and let it warm up before downloading or using it again. Condensation would form on the lens and viewfinder (I allow this to evaporate rtaher than trying to clean it). Do any of you shoot in extreme temperatures with your DSLRs? How do you keep your gear in good shape? My new Rebel XT is not sealed against weather nor are my lenses...is it a bad idea to take them out in extreme cold?