The battery is the biggest surprise for new film camera owners. Some cameras need one for everything, some only for the meter, and some don't take one at all. A few were designed around mercury cells that were banned decades ago, and their meters read differently on what you can buy now. Here's how to tell which kind of camera you're looking at and what to put in it.
Four kinds of camera
How much a camera depends on its battery decides what happens when the battery dies, and what a seller's "it fires" actually proves.
- No battery at all. The Olympus Trip 35 uses a selenium cell to set the exposure and needs no battery to work. The Mamiya RB67 body is fully mechanical with no battery, and the shutters live in the lenses.
- Battery for the meter only. The Pentax K1000, Nikon FM2 and Olympus OM-1 have mechanical shutters. Take the battery out and they still fire at every speed. You just lose the meter.
- A fallback speed. The Yashica Electro 35 sets its shutter electronically, but with no battery it still fires at 1/500. That's handy in bright sun and useless indoors.
- Battery for everything. The Canon AE-1 does nothing without its battery. The Minolta X-700 has no mechanical speed, even on Bulb. The Pentax 67 is completely battery dependent and won't finish its cycle when the voltage drops.
If you want the fewest battery worries, choose from the first two groups. A meter-only camera with a dead cell is still a working camera, and you can meter with a handheld meter or a phone app.
Why mercury cells mattered
Mercury cells hold a very steady 1.35 V for almost their whole life, only dropping in the last few percent. That flat output made them ideal for light meters, and many cameras and handheld meters were designed around the 625, PX675 and 400 mercury cells. A lot of those meters were built without voltage regulation, so they simply assumed 1.35 V.
Then mercury batteries were banned. In the EU, a 1991 directive stopped the sale of certain batteries with more than 25 mg of mercury, tightened again in 1998. In the US, the Mercury-Containing and Rechargeable Battery Management Act of 1996 stopped further sale of mercury batteries, with an exception for button cells under 25 mg. Today they're banned or restricted nearly everywhere.
So the cameras are still around and their cells aren't. Put a modern cell in an unregulated mercury-era meter and the different voltage, or a voltage that sags as it runs down, can give you wrong readings and wrong exposures.
What to put in a mercury-era camera
- Zinc-air cells. These are hearing-aid type cells that also run at 1.35 V with a similar flat discharge, so a meter reads them like the original. The catch is lifespan. Once opened to the air they last only a few months.
- Silver-oxide cells. They run at about 1.55 V with a very flat discharge. The output is steady, but the voltage is higher than the meter expects. That may not suit equipment without voltage regulation.
- Alkaline cells. Their voltage changes a lot over their life, so they're the least reliable choice for an unregulated meter.
- Adapters. You can buy adapters that hold a modern cell and use a Schottky or germanium diode to drop the voltage. They help, but a diode doesn't give a very accurate result when the current draw varies.
Whatever you choose, test the meter against a phone app or a handheld meter on your first roll, and adjust the film speed setting if it's consistently off. If the seller says the meter was recalibrated for modern cells, ask what cell it was set up for.
The Yashica Electro 35 case
The Electro 35 was designed for a 5.6 V mercury battery, which is now banned. A 6 V alkaline cell sold as PX28A or 4LR44 works with an adapter that fits it to the compartment. If the battery is missing or wrong, remember the camera still fires at 1/500 without power, so a seller's "it works" may only mean that. Ask for a slow exposure in dim light with a battery in.
6 V cells (4LR44, 4SR44 and PX28)
Many later cameras use a 6 V cell, sold under several names. The AE-1 takes a 4SR44 or 4LR44. The Pentax 67 takes a PX28, with PX28S and 4SR44 listed as later equivalents. These cells are still made, so there's no mercury problem. The letters tell you the chemistry. An L means alkaline and an S means silver oxide, which holds its voltage more steadily. Check the model page or manual for what your camera calls for, and look at the compartment in the listing photos before you buy.
Button cells for meter-only cameras
The K1000's meter runs on a single 1.5 V button cell, an LR44, SR44 or one of their equivalents like the S76, A76 or 357. The FM2 takes two S76 or A76 cells, or one 1/3N cell. Because these cameras only use power for the meter, one cell lasts a long time.
Check the compartment
Whatever the camera, a cell left inside for years can leak. Ask for a clear photo of the battery compartment with the cover off. Bright metal contacts are what you want. Green or white crust means a leak. Light crust usually cleans up. Heavy corrosion is a repair job, and on a battery-dependent camera bad contacts stop everything. Once you own the camera, take the battery out if you're putting it away for months.
What we'd buy
If batteries worry you, buy a mechanical camera. The K1000 and FM2 shoot on with a dead cell, and the Trip 35 never needed one. If you want a mercury-era classic like the Electro 35, budget for the right adapter or zinc-air cells and check the meter on your first roll. For electronic bodies like the AE-1 and X-700, get a fresh cell of the right type from day one and carry a spare. Our common faults guide covers the rest of what to check, and browse shows what's for sale now.
