Back in the day of film cameras, the "sensor" required no battery power to function and cameras were purely mechanical. Along came advancements in metering, though, and battery compartments became commonplace on camera bodies. At first, these were very small batteries. As film cameras added more complex circuitry to support their program modes, and then internal motors to advance the film, batteries got bigger.
Batteries for cameras used to be everywhere, but now they're increasingly hard-to-find. The racks which used to hold a wide variety of different camera batteries now hold different sized SD cards.
When my Leica M6 battery died, I made the rounds to every drugstore looking for a replacement. Although the camera is fully functional for taking pictures (it's an all-mechanical camera), the meter doesn't work without a battery. There may come a day when I don't need to lean on the meter as much, but for now it's a very helpful crutch.
|I opted for the 3V lithium because it's fewer pieces to lose.|
The camera is flexible as far as batteries go: the M6 takes either two 1.55 volt silver oxide batteries, which you stack together in the battery holder, or one single 3 volt lithium battery. I couldn't find either. Luckily we live in an online world, and diminishing local resources are still available over the internet. Even better, sometimes those resources are a lot cheaper. Surprisingly, this was the case with the Energizer 2L76 3 volt battery I needed. Mel Pierce Camera (through Amazon) offered a pack of *three* for $5.08. With free shipping. This price was less than I saw for a single battery of any type at the drug stores or anywhere else online.
At that price, I'm tempted to hoard them. (Lithium batteries can last a decade.) But Leica says that each of these tiny batteries will power the meter through about 4500 exposures. My three will last for more than a roll a film every day for a year. It seems reasonable to wait and hope that Mel Pierce still stocks them in 2015 because they're tiny enough that I'm likely to misplace them between now and when I've burned through the last one.
They don't make cameras like they used to, and they certainly don't make cameras with batteries this small anymore. (I mean, except for a Holga!)