If the battery fits, I use it. That’s my rule of thumb with my film cameras.
It is now, anyway. When I started collecting cameras again ten years ago I used to get wrapped around the pole over getting the battery just right. I’d read the warnings all over the Internet: you’ll get good exposures only when you use a battery with the voltage the camera expects.
Many old cameras were designed to take mercury cells for the steady voltages they held right up until the day they lost charge. But mercury cells were banned thirty years ago. Alkaline and silver-oxide cells are often available in the same sizes, but they have higher voltages. And in alkaline cells the voltage drops steadily under use. All of this is said to throw the camera’s exposures off a little.
At first, my solution was to buy Wein cell zinc-air batteries. They deliver a steady 1.35 volts, the voltage a lot of old cameras expect. Unfortunately, they last only a few months, where alkaline and silver-oxide cells can last years. And Wein cells cost more.
A couple times when I couldn’t get a battery of the right size, such as for my Yashica Electro 35 GSN, I bought a device that adapts an available battery. Such adapters sometimes even contain “bridge” circuitry to deliver the voltage the camera expects. But adapters can be pricey.
I soon tired of bleeding cash on batteries. Amazon sells batteries in bulk for good prices, so I bought a bunch of alkaline PX625 and LR44 batteries there. Most of my old cameras take one or the other of these batteries.
I’ve never had a lick of trouble with these batteries. My cameras return good exposures all the time.
Crucially, I almost always shoot negative films, which offer a lot of exposure latitude. Fujicolor 200 is my favorite, and it looks good when underexposed up to one stop or overexposed up to three stops. When I shoot black and white, I reach for Kodak Tri-X a lot, which yields usable results when misexposed by up to three stops in either direction. That’s more than enough to make up for any exposure challenges these batteries’ different voltages create.
Some of my cameras contain bridge circuitry to correct battery voltage. I turn to those cameras when I want to shoot slide film, which requires precise exposure.
But like I said, I shoot mostly negative film. So when a new-to-me old camera lands in my hands, I just drop in a battery that fits and get busy shooting.