Consider a lithium battery (CR-1/3N) for your F3. Lithium, unlike silver oxide or alkaline batteries, will take you deep into inhospitable temps. The LED of the F3 may not like such temps. I use the Nikon DB-2 (anti-cold, AA battery holder) occasionally but am afraid of breaking the connector/wire at the screw-in plug when temporarily storing the camera between shooting sessions, e.g. in a pack, etc. I can attest to the FM3a's reliability with and without batteries in temps well-below 0F. Fantastic camera in so many ways...except low-light meter reading.