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Though some photographers used to more tropical climates might think freezing (32 degrees F or 0 degrees C) is cold, neither the photographer or their gear should really experience any problems at that temperature. Just about all cameras, lenses and batteries are rated for use down to freezing (32 degrees F, 0 degrees C). However at lower temperatures there are a few things that may cause problems.
Most cold weather work will probably be done in the range from freezing down to 0 degrees F (-18 degrees C) since not too many places get much colder than that for more than a few days a year. However there are places that get down to the -40 degrees degree level (and -40 degrees F is the same as -40 degrees C). As I'm writing this in early January, the temperature in Fairbanks, Alaska is -31 degrees F/-35 degrees C, while the South Pole is at a relatively balmy-18 degrees F/-28 degrees C. If it gets below -40 degrees , I'd seriously think about staying indoors! Note also that "wind chill" factors don't apply to cameras, only to people.
Though most digital cameras are specified by their manufacturer only for operation down to a temperature of 0 degrees C (32 degrees F), most will work perfectly well at much lower temperatures. They aren't rated for lower temperature work because they aren't tested to fully meet all specifications at those temperatures and because there are some problems that can occur as detailed below 0 degrees C but most of those problems can be avoided. Electronics actually often work better at lower temperatures, so there's really no issue with the electronic circuitry.
The problems which may arise in very cold weather are usually either mechanical, related to LCD displays or related to battery issues. At just what temperature problems occur depends on the exact design of the equipment, but most modern cameras and lenses are just fine at -20 degrees C and can even be used down to -40 degrees C with a little care and attention.
Cameras and Lenses
Older mechanical cameras and lenses needed to be "winterized" for use at low temperatures. This involved taking them apart and removing the heavy lubricants from their mechanical parts. This was either replaced with a very low viscosity lubricant or no lubricant at all. Before they could be used again at normal temperatures, they had to be taken apart again and the lubricants replaced! Not very convenient and thankfully not necessary on today's cameras.
Modern autofocus cameras and lenses don't typically use much internal lubrication, and certainly not the viscous grease and oil used with earlier fully mechanical designs. Consequently they don't need any special winterizing for operation at low temperatures.
Cold Soaking
During operation, digital cameras actually generate their own heat. With some early digital cameras, after continuous operation for a while the batteries became almost to hot to touch! Modern cameras are significantly more efficient and generate less heat, but if you can keep that heat in the camera (by not cold soaking it), you may have fewer cold weather-related problems.
Cold soaking is leaving a camera out in the cold until every part is at ambient temperature - and it's likely to increase the probability of cold related problems. Since it can take quite a while for a camera to fully cool, if you only expose your camera to the very coldest temperatures when you're shooting, and put it in a pocket or a camera bag when it's not in use, you'll likely have fewer problems then if you leave it permanently hanging around your neck, fully exposed to the cold. It may not be that much warmer in your pocket or your camera bag, but every little helps. See also the section "Hand Warmers," below.
One thing to avoid though is bringing a really cold camera under your coat,especially if you've been sweating and the air trapped under your coat is very humid. This can happen even in very cold weather if you have a highly insulating coat and you've been working hard, for example by walking though deep snow. A cold camera/lens in a humid environment can result in condensation of moisture on both the optics and electronics, which is something best avoided. (See also "coming in from the cold" below).
Film
There are two problems which relate to the use of film at low temperature. The first is that at very low temperatures film can become brittle. If you bend it too much it may actually snap, so loading a camera needs care. The second problem is related to the verylow humidity of cold air. The dry air allows static electricity to build up on the film surface; this can be a problem during rewind. You can actually get a static discharge (sparks) inside the camera which leaves marks on the film. The slower you wind and rewind the less likely you are to run into problems from either brittle film or static discharge. Of course on many modern cameras, you have no choice about winding or rewinding speed, so there's not much you can do about it.
Memory Cards
There are very few reports of memory cards having problems in low temperatures. There are some industrial cards which are fully tested and specified for continuous use at temperatures down to -40 degrees C, but it seems that it's really not essential to use such cards. The Sandisk Extreme cards are specified for use down to -25 degrees C but even they are probably not required. Most users seem to find that even at the lowest temperatures most memory cards perform without problems.
I'd be a little wary of compact flash microdrives at low temperatures since they are mechanical devices and are more likely to have coldrelated problems. Fortunately, few cameras these days use microdrives.
LCDs
LCDs (Liquid Crystal Displays) are affected by low temperatures. They may lose contrast (grey out), change the displayed information more slowly, and become quite sensitive to touch (if you press on them they may change color). This is reversible--once they warm up, they should be fine.
Plastics
At normal temperatures plastics are...well...plastic. The will bend a little and some mechanisms depend on that (e.g. plastic hinges and catches). At very low temperature splastics may become quite brittle and will break before they bend. This means you need to be quite careful when opening any plastic camera doors (for example: battery compartment doors) to avoid accidental damage.
Beware of Metal
Touching bare metal at sub-freezing temperatures with bare hands can be quite a painful experience. Moisture on your hands can freeze and "glue" you to the metal surface! Since most modern cameras are either plastic or plastic-covered, this isn't too much of a problem when handing cameras, but touching bare metal tripod legs with ungloved hands can be a problem. You can get insulating sleeves for tripod legs (or you can use pipe insulation) and if you use a carbon fiber tripod you'll also be safe. If you need more dexterity than you get wearing heavy gloves, to wear thin silk glove liners at low temperatures--don't use your bare hands!
Battery Power
Batteries lose a lot of their power at low temperature. This applies to all batteries but some do better in low temperatures than others. The best cold performance probably comes from primary (i.e. non-rechargeable) Li cells, followed by NiCd, NiMH and Li-ion rechargables. They should all be fine down to -20 degrees C, though they will certainly have a lower capacity than they do at higher temperatures. Most will work for a while at even lower temperatures. If they get really cold and become exhausted they will usually regain power if warmed back up, so take 2 or 3 (if not more) batteries out in the field with youand switch them between your camera and a warm pocket and you should be OK.
For some camera systems an external battery pack is available which connects to the camera via a cable. This means you can keep the batteries warm under your jacket, but the cable between the battery pack and the camera can be inconvenient. Note that alkaline batteries and particularly rechargable alkaline batteries tend not to perform well in very cold conditions and so should probably be avoided.
Hand Warmers
One way to keep your batteries warm is to wrap a small hand warmer around the section of the camera that contains the batteries (usually the handgrip for DSLRs). Hand Warmers are small packets containing iron powder mixed in with a few additional chemicals such as charcoal and salt. When the packet is opened and exposed to air, oxygen reacts with the iron (to form iron oxide - which is rust) and that reaction releases heat. The reaction is quite slow and the heat can last anywhere from 6 to 24 hours depending on the size and design.
Since these are intended to be used to warm hands and feet, they don't get really hot, so they are usually safe to use next to a camera. Carrying a few extras for your hands and feet might be not be a bad idea too! If you don't want to wrap one around your camera and you keep your camera in a bag when you're not shooting (see "cold soaking," above), you can place a hand warmer in the bag next to the camera. It may not raise the temperature in the bag much, but even a few degrees can help.
Exposure
No, I'm not talking about the medical condition (at least I hope not), but the influence of temperature on photographic exposure. Generally it's insignificant for both film and digital cameras. The basic sensitivities of film and digital sensors won't change much over the temperature range that you are likely to encounter. Though cold doesn't appreciably change intrinsic film speed, lower temperatures may significantly lessen reciprocity failure for film so some adjustment of normal reciprocity correction factors may be needed for long exposures.
In very snowy conditions, where just about everything is white, you may need to dial in +1 or +2 stops of exposure compensation if you want white snow to be white, and not an 18 percent middle grey. Remember that most auto exposure systems assume the scene they are metering is 18 percent grey and expose accordingly. Some may correct for the brightness of snow in full sunlight when using an evaluative (matrix) metering mode, so in that case you might not need exposure compensation. Those shooting digital should review their images and check the image histogram to make sure that the exposure is giving the desired results. If all else fails, you can always fall back on incident metering!
In falling or blowing snow a lens hood can help to prevent problems with snow on the front element of a lens. Since snow tends to reflect the sky it can take on a bluish cast on a clear, sunny day, especially in shadow areas, so a slight warming filter may help when shooting film. When shooting digitally, be sure to change your WB to open shade, which assumes a warmer hue due to the effect of a blue sky. Even with digital, since snow has a very high UV reflectivity (80-90), a UV filter isn't a bad idea.
Coming in from the cold
A major problem with cold weather shooting can occur not while you are outside, but when you come back into a heated area. Very cold air is very dry, but air in a heated room usually contains moisture. In fact, many homes use a humidifier during the winter months to keep the air moist because it's more comfortable for people. If you bring a very cold camera and lens into a room with warm, moist air, moisture will condense out of the air and onto the cold surfaces. The problem isn't so much the moisture you may see on the outside of the camera or lens, but the moisture which condenses on internal parts. Electronics and moisture don't mix well and you really don't want condensation on the inner elements of lenses either.
The good news is that the moisture will eventually evaporate if the equipment is allowed to warm up to room temperature, but it can take a long time. You can gently warm the gear with a hair drier on a low setting to speed things up, but a much better procedure is not to let the moisture condense in the first place. If you do get condensation on a camera, remove the batteries and don't replace them until you are sure the camera has dried out. Just because a camera is "off" doesn't mean that electronics are safe from damage. Many cameras are just in a "sleep" state when off, with power still applied to some components.
You can avoid problems if you seal your camera gear in an airtight plastic bag before you bring it inside. It will then be surrounded only by the very dry air from outdoors.You may get some condensation on the outside of the bag, but the camera/lens will slowly warm up in dry air inside the bag and will stay dry. Self sealing freezer bagswork well for this, but any bag which you can seal will be OK. Just be sure to put the camera/lens in the bag before you go indoors. Once you're indoors, it's too late!
All images © 2000-2006 Bob Atkins
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