Suggestions for Photography at Temperatures Below Zero
by Jeffrey Sward
Making photographs outdoors in temperatures well below zero presents some unique issues. Experience making photographs at -30°F (-34°C) in Barrow Alaska has revealed the following suggestions:
Hypothermia is a fancy schmancy word for freezing to death. Hypothermia is something to be avoided. Most photographers make much better pictures when still alive. Hypothermia is best avoided by proper clothing. The following list of clothing is a starting point. Dressing in multiple layers adds warmth. This is not a list of options. Everything on the list, or its equivalent, needs to be worn at the same time.
Frostbite occurs when an area of the body freezes and ice crystals form within the cells. These ice crystals cause the cells to rupture, leading to cell death. Eventually doctors will want to remove affected areas surgically. Popular areas for frostbite are toes, fingers, and exposed areas of the face. Frostbite is a good thing to avoid. There is an interesting article on frostbite at medicinenet.com. Steps mentioned above under hypothermia also help avoid frostbite. It is a good idea avoid exposed skin. Monitoring skin color is also a good idea, such as:
Generally soaking areas of any unusual color or numb areas in warm bath water is a good practice.
If you have been outside for a while and the ends of your eyes start stinging, then probably the moist parts of eye lids are freezing. This is now a good time to go inside.
Condensation occurs when warm moist air comes in contact with a cold surface. Water then appears on the colder surface. Condensation is popular on car windshields at night. Condensation is observed when putting room temperature eyeglasses very close to an open mouth and saying "hah." Very moist +98°F air comes in contact with +70°F glass.
Condensation combined with winter gets interesting. Frost is condensation which has frozen.
One bit of good news for photographers is that winters tend have very dry air. Ask your buddies from Omaha to tell you about the setting on their furnace which on "humidify" in the winter and "dehumidify" in the summer. Winters are dry, summers are wet. Bread are square, pie are round. Therefore, there is not very much condensation due to ambient outside air. Also, when temperatures get below zero Fahrenheit, it becomes "too cold to snow" and there is even less humidity. Thusly, if we have a camera indoors in moist +72°F air and we take it into -30°F dry air, generally this will not produce condensation, because the outside is both cold and dry, and at this point the camera lens and camera filters are warm. Also, several people recommend keeping your camera inside your parka until picture time. This will keep the batteries warm (see below) and will generally not cause condensation unless you are sweating like a pig.
Now for all of the bad news.
After taking pictures for a few minutes in -30°F all equipment is also -30°F. The camera itself, the lens barrel, the glass in the lens, and any filters are all now -30°F. (Also the battery, see below). We are still avoiding condensation since the outside air is dry. However, human breath is always very moist. At this point we are hoping the photographer has avoided hypothermia and is still alive. The photographer, still being alive, will be breathing. Any breath expelled directly at a lens or filter at -30°F will cause condensation, which will immediately freeze on the glass filter or lens. (Ice is now on the filter or lens.) From this point forward pictures will be impossible until the camera-lens-filter combination is brought inside, warmed above freezing, and the lens and filter are cleaned. As always, use lens cleaning fluid and lens cleaning tissue to clean the lens or filter. It is really easy to tell if the lens or filter is warm enough to clean. Lens cleaning fluid will also instantly freeze when applied to the filter or lens when the lens or filter is too cold.
After working outside and avoiding condensation on the lens and filter, bringing the equipment inside will immediately cause condensation (frozen or otherwise) on the lens or filter because the glass parts are still -30°F and the inside air is warm and relatively moist.
In summary, when photographing in cold temperatures:
Older photographers will remember when cameras were completely mechanical, except perhaps for an advisory light meter. Mechanical cameras operated in cold temperatures until the camera got so cold that the grease on the mechanical parts froze. Those days are over.
Nearly all cameras today are completely electronically controlled. No battery means no picture. Therefore, camera battery management in cold temperatures is crucial for the camera to operate at all.
It is often stated that "cold weather drains batteries quickly." This is at best an oversimplification, but in reality is essentially not true. However, the effects of cold weather make it appear that batteries drain quickly. Think of a battery as a reservoir which holds electrons instead of water. In order for the electrons to move from the reservoir to the camera, they must pass through a gate. The colder the temperature, the more the gate closes. When it gets cold enough, the gate is completely closed, and no electrons from the reservoir can reach the camera. There are plenty of electrons left, but they are trapped.
Try this simple experiment: take your favorite camera and insert a brand new fresh battery. Press the battery check button. It should show a fully charged battery. Now take the camera with battery and put it in your freezer for two hours. My freezer is +10°F, which is a full 40 degrees warmer than -30°F. After two hours in the freezer, immediately press the battery check button. It should show the battery is deader than a door nail. Now leave the same camera and battery at room temperature for 24 hours. Press the battery check button. Presto! It should again show a fully charged battery. The cold did not "drain the battery." The cold merely made the electrons still in the battery unavailable.
Regardless of the physics involved, after some minutes at -30°F your camera battery will become useless. Therefore, it is advisable to travel will a fairly large number of spare batteries. The cognoscenti store their spare batteries either indoors or in an inner pocket next to their body heat in order to keep the batteries warm. However, the "dead" battery may indeed be perfectly good when brought back to room temperature. It may be possible then to rotate back the first battery into the camera when the first battery is back to room temperature. Thusly, it is quite possible to continue rotating a set of batteries by keeping several at a time at room temperature.
If you own a camera which allows an external battery pack, then use it. Obtain the longest power cord possible. Keep the external battery pack warm under your parka, and route the power cord around the bottom of the parka or through the top of the zipper to the camera. The warm battery pack should last about as long as it would at normal temperatures.
Depending on where your battery compartment is located on your camera, it may or may not be advisable to change the battery outdoors. If delicate interior parts are exposed by opening the battery compartment, discretion would indicate indoor battery changing.
Changing Film or Digital Storage Cards
The camera battery has managed to stay alive long enough to finish the roll and run the automatic rewind. So now is the time to change the film, right? In a pig's eye! Changing film at -30°F is an invitation to trouble. First, even with tight gloves, it is unlikely that enough dexterity will be available to open the camera, remove the old film, and load the new film. Removing the gloves invites frostbite. Suppose some super-human dexterity is possible to manage film changing wearing gloves. During the changing operation, the entire inside of the camera will be exposed to the elements. -30°F will certainly damage things like the shutter mechanism. Similar reasoning applies to avoiding opening up digital cameras at -30°F in order to change the digital storage card.
In colder climates the difference between day and night temperatures in winter is often very small, such as 10 degrees or less. The sun does not warm the air up much. However, it does somehow warm people up slightly. Sun is a good thing, but ultimately it will not make much difference for things like hypothermia.
Humans will experience any given temperature as much colder when a wind is blowing compared to still air. Some mad scientist somewhere created some bizarre calculation to show when the wind is moving at x miles per hour and the air temperature is at y then humans will experience the temperature as equivalent to z where z is less than y. Do not believe it for a minute. It feels much colder than the scientist predicted. At -30°F, a wind of any significance will freeze your rear off. Hypothermia and frostbite become much greater risks with increased wind. Besides, there will always be snow, which will now start blowing. How many pictures of blowing snow do you need?
The Definition of "Inside"
"Inside" in the context of this discussion generally refers to a heated building. A lot of guys and gals will use a vehicle as the inside warm area. This works great. However:
Limiting Factors Summary
Putting this all together, outdoor picture taking in cold weather stops when any of the following happen:
Some mad scientist somewhere can tell you why "metal conducts heat and cold." In practice this means that when using a metal tripod, if you grab the metal tripod legs, they will be extremely cold, even when wearing gloves. Incredible differences can be made by covering the metal with some nonmetallic substance, such as water pipe insulation or even duct tape. Real tripod manufacturers make accessory leg wraps for their models. For example the Bogen-Manfrotto part number is "3430 Leg Protectors" or "3431 Leg Protectors."
Wooden tripods avoid the cold metal problem, but might not take well to cold weather and snow.
Similarly, regular tripod legs sink on snow. Real tripod manufacturers make accessory snow shoes which fit over the tripod legs. The snow shoes look ridiculous, but they really work. For Bogen-Manfrotto the part number is "230 Snow Shoes."
This section is about exposing film. The other type of exposure is covered under the "hypothermia" section.
In practical terms, film will record a value range of 7 stops. This means that if a meter reading of the darkest part of a scene compared to a meter reading of the lightest part of scene is 7 stops or less, and the camera is set to the average of the light and dark meter readings, then the film will be exposed "correctly." The gray tone in the middle of the 7 stops is called "18% gray" or "middle gray." There are three stops of dark tones below middle gray and three stops of light tones above middle gray.
Exposure meters are calibrated to assume that a "typical scene" will "average" to 18% gray. This scheme generally works well for taking "typical scenes" such as a meadow with clouds in the sky, or a portrait of your Aunt Mildred. However, arctic scenes are very atypical. An arctic scene consists of a lot of snow, bright sky, and an occasional dark splotch of something like a rock. Left alone, the exposure meter will assume everything "averages" to 18% gray and turn the entire picture middle gray; i.e. the snow becomes middle gray rather than white (or probably middle blue because of other optical properties beyond the scope of this discussion.) The exposure meter has "placed" the white snow in the middle gray tone, making the whole picture too dark. The picture has not gotten enough light (enough exposure). We wish to "place" the white snow somewhere in the three stops we have available for light tones above middle gray. However, we do not want to use up all of the three stops since there will be a lack of detail in the snow if we do.
In order to compensate for all this, when a picture is predominately snow, open up the aperture between 1 1/3 and 1 2/3 stops (add more exposure). Example: When pointed at snow, the meter suggests 1/125 at f8. Instead, use 1/125 at f5 or 1/125 at f4.5. (f5.6 is one stop more than f8). Equivalently, when pointed at the snow, leave the aperture alone and slow down the shutter speed by 1 1/3 to 1 2/3 stops. Example: When pointed at snow, the meter suggests 1/125 at f8. Instead, use 1/50 at f8 or 1/40 at f8. (1/60 is one stop more than 1/125).
On my Canon EOS-1, when on manual metering, the cute arrow on the exposure scale goes up for overexposure and down for underexposure. So, for a manually metered snow picture, place the magic arrow 1 1/3 to 1 2/3 stops above the center mark. If it is possible to point the meter at a middle tone, do not change the exposure from the meter indication. Care must be taken to understand how your meter works, such as whether it averages, center weights, spot, matrix, etc. in order to interpret the light readings.
Transparencies (slides) have less exposure latitude than negative film. Negative film usually has three-stop overexposure latitude with no loss of image quality. We deftly note that the three-stop overexposure latitude is less than the 1 1/3 to 1 2/3 compensation, so we can use this film characteristic when shooting negatives. Thusly, it is practical to rate negative film at 2 stops lower than the rated speed at all times in arctic conditions. For example: if the box rates the film at ISO 200, set the camera at ISO 50. In this way, when metering snow, the exposure will be "normal" because of the need to compensate is built into the ISO rating we dialed into the camera. When metering a middle tone, the exposure will be 2 stops overexposed, which is well within the film latitude.
Therefore in summary:
The photographer cum laude of aurora photography is Dick Hutchinson. Dick has a very informative aurora web site.
Some additional aurora notes or differences from Dick's notes:
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