Mercury battery metering
Many classic meters were calibrated for banned 1.35V mercury cells. A modern battery at a different voltage can throw the meter off. Choose your replacement to see the likely effect and a fix.
Cameras with a bridge or feedback circuit (many later models) are barely affected — check yours. When in doubt, meter a grey card and bracket, or use a handheld meter.
About this tool
Many classic camera meters were calibrated for banned 1.35V mercury cells. A modern replacement at a different voltage can shift the meter. Choose your replacement cell to see the likely effect and how to compensate.
How to use it
- Choose the replacement cell you are using.
- Read how it affects the meter reading.
- Apply the suggested film-speed compensation, or fit a voltage adapter.
- When unsure, meter a grey card and bracket your exposures.
FAQ
Is every camera affected the same way?
No. Cameras with a bridge or feedback circuit are barely affected, while simple voltage-sensitive meters shift the most.
What is the most accurate fix?
An MR-9 adapter that steps 1.55V silver cells down to 1.35V, or a zinc-air cell that is close to the original voltage.