Start with the model, not a generic “camera battery”
Film bodies use several different power architectures. Some need a 6V photographic stack cell for the whole camera. Others are fully mechanical and only use a button cell for the light meter. A few vintage meters were designed around 1.35V mercury cells that are no longer sold.
Open the device page for your exact model when we have one. Guessing from a neighbour’s SLR is how people buy the wrong voltage.
6V photographic cells (4LR44 / PX28 family)
Canon AE-1 and AE-1 Program take one 6V cell in the 4LR44 / PX28 form factor. Canon’s museum listing for the AE-1 names a mercury 4G-13 or alkaline 4LR44; the AE-1 Program lists 4LR44. Modern packs may say PX28, 4SR44, A544 or PX28L — same outer size, not always the same chemistry.
See 4LR44 and PX28 vs 4LR44 before substituting labels.
Meter-only and dual-option button cells
Pentax K1000 uses one LR44 / SR44 for the meter only — the shutter is fully mechanical and works without a cell.
Minolta X-700 needs power for shutter and meter: two LR44, two SR44, or one CR13N (CR1/3N) per the manual. Do not use mercury MR44 lookalikes.
Mercury-era 1.35V cells (PX625 and friends)
PX625, PX13 and MR9 were 1.35V mercury cells for meters and cameras (Olympus OM-1 is a common example). Alkaline lookalikes can fit and still meter wrongly.
See PX625 and PX625 replacement options for zinc-air and adapter paths. Do not treat a 6V AE-1 cell as a PX625 substitute.
Instant cameras
Fujifilm Instax Mini cameras usually take AA alkaline cells — see the Instax battery guide. Classic Polaroid packfilm is a different architecture (battery in the film pack).
Digital cameras (AA digicams)
Some compact digicams take AA cells with model-specific counts and named NiMH SKUs (for example Coolpix L120 4× AA / EN-MH2, PowerShot A-series 2× AA). That is a different category from film bodies — use the Digital cameras browse and digital camera batteries resolver, not this film-cell chart.