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Digital cameras are electronic devices and consequently need a steady supply of electricity. With today's technologies, their needs border on the prodigious and often sneak to the far side of the border. That power has to come from somewhere, and the places of choice are two—from self-contained batteries or from utility-supplied electricity through an external transformer, the ubiquitous power brick.
Unlike camcorders, the batteries for most digital cameras are standard sizes. Most digital cameras use standard AA or AAA batteries, typically about four (the number needed to get enough voltage for conventional logic circuits). Most manufacturers generously include batteries with their products.
Digital cameras are high-current devices. They cannot use standard or heavy-duty batteries based on carbon-zinc technology. They require alkaline or rechargeable cells. In fact, some manufacturers warn to use their products only with rechargeable batteries, such as nickel-cadmium cells or nickel-metal hydride (NiMH) cells. Chapter 31, "Power," discusses these battery technologies in detail.
Batteries may seem to behave strangely under the high-current demands of digital cameras. For example, while alkaline cells may last long enough to capture a dozen images, rechargeable cells of the same size may work for 100 images or more. Subtle differences in battery construction used by different brands can have a big effect on battery capacity. Some manufacturers' cells may appear to fail after only a few exposures. Such batteries are far from dead, but they can no longer generate the high current your digital camera requires.
The high-current demand also makes battery life unpredictable. You'll always want to carry spares.
When loading fresh batteries in your camera, never mix battery technologies or even battery brands. Different battery brands may use slightly different physical constructions or even different chemical mixes with the possible result of the internal resistance of the brands of cells being different, resulting in some cells working harder (and draining faster) than others. In other words, make sure the cells you use are identical.
Nearly all digital cameras make provisions for plugging in an AC adapter. Many, however, make the AC adapter an option. If you work primarily in a studio, the AC adapter is a worthwhile expense because it will save you the cost of batteries and the time needed to change them.
You can substitute a generic AC adapter for the official one offered by the camera manufacturer. Check your camera's specification sheet to determine the current your camera requires as well as the voltage and polarity of the AC adapter. Often polarity is described graphically with a plus or minus sign pointing to a dot inside a circle. The dot corresponds to the central conductor of the power connector. The only important issue is that the diagram that's shown in your camera's specifications match that of the AC adapter you choose.
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