The Sub Club

METER OPERATIONS AND LIMITATIONS

BATTERY DEPENDENCY

Although one manufacturer (Ricoh) produced a solar-powered camera, the typical modern camera uses a battery to provide the needed electricity to the metering system. The battery may also provide electricity to other camera featurtes. But the use of batteries is not without limitations. First, batteries wear out; through use and time they become depleted and useless. It's normally no problem to replace them, but batteries are known to wear out at the most inopportune times, for example during a wedding when time is of the essence or in a wilderness five miles from the nearest road. Obviously it's a good idea to keep a spare battery handy, but check it periodically since batteries can be depleted just sitting around. When not in the field, keep the spare battery in the refrigerator; the cold temperature slows down the chemical reaction which occurs in the battery and lets it last longer.

There is a more insidious problem related to batteries than simply whether they are dead or not. It's easy to spot a dead battery because it will not provide any sort of exposure readout, but if the batteries are only weak and not quite dead they may contain sufficient power to indicate an exposure reading -- although an inaccurate one. The unwary photographer has no clue that the exposure reading is incorrect until the improperly exposed pictures are returned from the lab. So make sure to check the camera battery regularly. If your camera doesn't have a built-in battery check mechanism, buy a separate checker from an electronics store or replace your batteries regularly according to their use. Also don't just assume that since a battery is new or unused that it contains a good charge. Time spent sitting on a store shelf deteriorates batteries and they should be checked for potency before they are taken out of the store and used in the camera. Sometimes there are holes placed in the back of the battery package in order to check the condition before the purchase is made. With some of the more specialized batteries costing over $15 each, these precautions will prove well worth the effort.

Batteries can also cause exposure errors through leakage and corrosion of the terminals. It's a good idea to periodically remove the batteries and check them for cleanliness. If a problem is found, replace the batteries and clean the camera terminals with a standard pencil eraser. Manufacturers typically recommend removing the batteries from any equipment that will go unused for more than a couple of weeks in order to avoid this problem. If you have ever had a battery corrode inside a camera you know the importance of this ounce of prevention.

Another problem with batteries pertains to cold weather. Batteries, like water, freeze when cold and this can result in no exposure reading from the camera or, worse, an inaccurate one. To avoid this problem, in below-freezing temperatures keep your batteries as warm as possible. A common approach is to keep the camera underneath your coat when not in use. Except in the most severe of conditions this approach will provide sufficient warmth for the batteries but can lead to another problem -- condensation.

By removing the camera from the warm, humid air under the jacket, moisture can condense and freeze on the lens and the viewfinder in a matter of seconds. If this happens never try to rub or scrape of the ice; you could end up scraping the surface of the lens. Warm the camera until the condensation evaporates and them return the camera to the cold more gradually. When ready, shoot fast to avoid the battery freezing. Weak batteries are especially susceptible to the cold, so insert new batteries whenever cold weather photography is on the menu.

Some manufacturers produce remote battery packs for their meters and motor drives which allow the photographer to operate the camera under cold conditions while the batteries are kept warm by body heat. Home-made models work equally as well. Under severe or prolonged arctic conditions it is advisable to use cameras and meters which are not battery dependent.

A list of the major types of batteries to which the photographer may be exposed will point out the strengths and weaknesses of each.

Carbon-Zinc -- the common, everyday "flashlight" battery with which we are all familiar. It's main selling point is its low price.
Alkaline -- the alkaline cell has several advantages over the carbon-zinc battery. First, it has better storage life; it survives just sitting on the shelf much better. In addition, it can be used in lower temperatures than any of the other battery types.
Lithium -- lithium batteries are now found in several cameras and offer incredibly long life on the shelf and in the camera.
Mercuric Oxide -- mercury batteries also offer outstanding shelf life. They are not as useful in cold weather but when stored retain their potency for years.
Silver Oxide -- the silver oxide battery also offers outstanding shelf life over the long haul. Unfortunately, it is a poor performer in cold climates.
Nickel-cadmium -- the nicad is economical because it can be recharged hundreds of times. They have good cold weather performance but loose their charge quickly, relative to the other types, when sitting on the shelf.
Zinc-air -- this type of battery is common in hearing aids. It has two or four holes on one side that are initially covered. Removing the plastic tab let's air in and activates the battery. The biggest problem is that it takes about 30 minutes to get the voltage up to speed when the tab is removed.

Chose the type of battery which offers the best performance given your shooting conditions.

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