Cold weather photography presents numerous challenges to photographers and their equipment. From drained batteries to frostbit fingers, cold weather photography is a completely different prospect than hot weather shooting. While there are some simple solutions to most cold weather photography problems, these solutions may not be the ones you would first think about.
Condensation is a photographer's nightmare. Just like a pair of eyeglasses fogging up when changing temperatures rapidly, a camera lens (and the inside of the camera) can fog up with condensation. Condensation is water forming on surfaces that are significantly colder or warmer than the air surrounding it. Technically, this means that if your camera goes into an area where the air is warm condensation will form if the camera is colder than the dew point. The opposite is also true. If your camera goes into a cold air area and the camera is warmer than the dew point then condensation can form.
How to Avoid Condensation?
The basic way to avoid condensation is to gradually bring your camera through these extreme temperature changes by sealing it inside a bag containing air the same temperature as the camera is acclimatized to. This way, any condensation forms on the bag instead of the camera as the air and camera gradually equalize to the new environment. In practice, this usually results in the photographer freezing in their car because they don't want to wait for the camera to cool off when he/she gets to the photo location.
A Hidden Cause of Condensation
Another source of condensation is the photographer. If you breathe on your camera you risk fogging it. The heat from your eye could also cause problems on the viewfinder. If your viewfinder fogs due to photographer body heat it is almost always only an inconvenience that does not affect the rest of the camera. You should, however, refrain from putting your camera in your coat as this could raise the temperature of the camera and lens itself enough to create problematic condensation.
Remember that condensation can form inside the camera as well. Beyond the moisture not agreeing with any electronic parts, the moisture could freeze in very cold conditions and completely ruin the camera.
Batteries lose their charge more quickly in cold weather. When shooting in cold weather it is essential to carry spare batteries for all of your equipment. Lithium batteries are a good choice as they are better at holding a charge than the older chemical compositions to begin with. You can also keep the spare batteries in your coat pocket or another relatively warm spot. However, be extremely careful not to let the batteries be too warm as this could cause condensation when they are placed back into the cold equipment.
We all know to wear a coat when we go outside in the cold, but we often forget about our hands and faces. For your face, consider a ski mask to reduce the amount of skin exposed to the wind and cold. This can also help reduce the amount of water vapor you breathe onto your camera. A photographer's fingers and face are the most endangered in cold weather shooting. Often a photographer will take off their gloves while shooting in order to better handle the camera. This exposes your fingers not only to the cold but also the wind. Even if the ambient air temperature is not below freezing, the wind chill may be cold enough to cause frostbite.
Fingers cause a bit more problems for photographers. Fear of dropping the camera and difficulty in managing the controls with heavy gloves often leads photographers to forgo gloves altogether. This leads to quickly numb fingers and is a fast track to frostbite. Depending on how cold the conditions are, you may even be at risk for your fingers freezing to the metal on the camera. Layering your gloves is an excellent solution to frozen fingers. Wear silk or other fine mesh gloves first (even women's nylons with a few extra seams make great first layer gloves). Over these gloves add a pair of fingerless crafter's gloves. These not only add warmth but can also help cut down on hand fatigue. The final layer are your normal cold-weather heavy gloves. These will be removed whenever you are shooting so a cord to hang them around your neck is needed to prevent losing them. Your fingers will still get cold with the crafter's gloves and under gloves (but more slowly). Try keeping a hunter's chemical heat pack in your coat pocket for quick reheating of your hands in between frames.
Even when wearing very well insulated boots, your feet can become damp from perspiration or a poorly placed step that puts you in snow higher than your boot tops. Wet skin is in major danger of damage from cold. Keep extra socks with you at all times for emergency changes. Keeping a couple of kitchen dish towels with you will also allow you to dry off your feet before changing socks.
In cold conditions, almost any surface can be covered in ice. Photographers are notorious for not paying attention to their surroundings while they are focusing on a subject. Be sure to pay attention to where you are stepping and wear footgear with good traction in order to avoid a nasty fall.