Cameras tend be used very intensively over a short amount of time, and
then stored for a while before their next use. This has resulted in lithium
batteries dominating the market for camera batteries. Lithium batteries
can provide a lot of relatively high voltage power, and do so quickly. This
is important when the battery needs to power the film motor, the range finder
electronics, the powered zoom and a flash, nearly all at the same time.
Lithium batteries also have a shelf life of 10 years of more, which means
that the battery doesn't loose any of charge when it is not being used.
Most of the camera batteries available today are quite mature. The most common sizes come with labels such as CR123, CR2, 2CR5 or CRP2P. All of the big brand battery manufacturers offer these batteries, although some electronics companies (such as Panasonic), and some film companies (such as Kodak) also offer photo batteries under their brand. Because of the relative maturity of this type of battery, there are only small differences in performance between the camera batteries sold with brand names you would recognize. As such, there are great opportunities to save money by shopping around.
One more recent battery is the CR-V3. It is a 6 Volt lithium battery that will fit into a battery compartment the same size as two AA batteries. Because it doesn't waste the space between two cylindrical AA cells, it has more space for electricity producing chemicals, and will thus last longer than a pair of lithium AA batteries.
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