A long time ago, we got our first digital camera and boy, did it eat batteries. Not only was it annoying, it was expensive, and as you well know -- we're cheap (uh, thrifty). Thus, I got the bright idea to get some NiMH rechargable batteries, since in my youth I had used the older NiCd rechargables to good effect in many devices.
The new NiMH rechargables have a huge edge over the now-obsolete NiCds, and that's capacity. A NiCd AA only holds about 1Ah worth of "charge", while the NiMHs hold anywhere from 2 to 2.7Ah so they last 2-3 times longer.
Since our camera was eating batteries like crazy, we got the highest capacity NiMHs we could find. We were all set, right?
Wrong. High-capacity NiMHs have this nagging little problem called self-discharge. You can charge them up but if you don't use them for a week, they're half dead. A month later, they're now useless and need recharged even though you didn't use them much, or at all! Worse, our camera's "low battery indicator" would activate after taking only a few pictures and die soon after. You see, it also turned out that NiMHs are about 1.2 volts while throwaway alkalines are about 1.5 volts. .3 doesn't sound like much but our camera was not happy about the difference.
We weren't happy, either.
This was several years ago and times have changed. Digital cameras (and other devices) are now designed to operate on both 1.2 volt NiMH and 1.5 volt alkalines, and battery makers have solved the self-discharge problem, if you know what to look for.
You can now get "LSD" or Low-Self-Discharge NiMH cells, but you have to check carefully what you're getting because the labeling is not clear. If the package says "Pre-charged" or "Hybrid" or "Lasts 6 months" or "Holds a charge for 1 year", those are LSD cells. If it isn't labeled as such, they are ordinary NiMHs and you should probably steer clear.
There's just one catch: LSD cells do not hold as much energy -- only about 2/3 as much as high-capacity NiMH... but the tradeoff is soooo worth it. The only situation where high-capacity wins is if you're charging and then totally discharging them the next day, such as a professional photographer doing a wedding or something. Otherwise, LSD is superior in every other application. And in some cases, LSD even beats throwaway alkalines! More on that later.
Though Lemontree was skeptical after our last attempt at rechargables, I put down the money for the best LSD cells available. That's where the funny name comes in: Eneloop. Yep. They're from the Japanese company Sanyo, so maybe something was lost in the translation. But in spite of the funny name, they're the best LSD for all sorts of technical reasons that would probably bore you so we'll leave it at that.
Incidentally, Duracell Pre-charged NiMHs with white tops are actually rebadged Eneloops, so if you can find them at a store they're great (Eneloops can only be ordered online). Pre-charged Duracell black-top, Energizer Hybrid, and Rayovac "4.0" are also LSD and also work fine, but are not quite as nice. I'm told Kodak also makes some LSD but I don't know what they're called.
Anyway, I have a small LED flashlight I carry in my pocket every day that takes an AA cell. With an alkaline, the brightness would start to dim within minutes as the battery was used up. With an LSD NiMH cell like an Eneloop in it though, it stays full brightness for over an hour. That's because an alkaline battery's voltage drops linearly, while NiMH voltage stays steady for most of it's lifetime. And, of course, I can feel more comfortable actually using my light instead of worrying about spending piles of money on batteries and polluting the environment with piles of batteries. Same goes for the camera, we no longer have to be stingy about using the flash so our pictures have better color saturation and are less blurry since the the camera can use a faster shutter speed.
I suspect Lemontree will remain unconvinced until we have logged more hours on the camera using the LSD cells, but Canon (who made our camera) actually says we should be able to get more pictures out of the NiMH than with alkalines (same reason my flashlight lasts longer, the voltage curve), so I remain optimistic.
So... save money, save the environment, use LSD!
...I think I just told everyone to do acid.