 Mercury batteries are no longer available, but there is a solution!
The exposure meter in many classic SLRs and Compacts were designed to use Mercury batteries, because they maintain a very accurate 1.35 volt over their entire life.
This in turn means very accurate exposure. Mercury batteries are no longer made since mercury is now considered unsafe and an environmental hazard.
Affected equipment include: Minolta SRT, Canon FTb, Olympus OM1, Pentax Spotmatic, Rollei 35, Konica Autoreflex, and accessories such as Gossen Exposure meters, and more.
Why can’t you just use another battery the same size?
By merely substituting the Mercury Battery with another type of the same size you risk causing damage to the meter system, not to mention inaccurate exposure (up to 2 stops or more). Cameras using mercury batteries need a constant 1.35 volt to perform accurately.
- Alkaline batteries are rated at 1.55 volt. They do not maintain a constant voltage and the meter accuracy then suffers, but worst of all, Alkaline button cell batteries can and do cause corrosion which may irreversibly damage the meter system.
- Zinc-Air batteries were produced as substitutes, but our experience is that they often leak and cause corrosion. They are expensive and frequently hard to obtain. On top of that they have a limited life after being activated.
- Silver-Oxide batteries are also rated at 1.55 volt. This is too high, BUT, they have similar characteristics to Mercury batteries in that they maintain the constant voltage necessary for meter accuracy. They are nearly leak proof, safe, and readily available.
So - how can we use Silver Oxide Batteries?
At Camera Check Point we carry out a small electrical modification to reduce the voltage. Where necessary we fit a small ring or adaptor to accommodate the readily available MS76, S76E, or SR.44 Silver Oxide battery. The meter is then checked and recalibrated as necessary.
The update can be carried out as a separate service, and is always performed whenever a camera is presented for a Major Service or overhaul.
|
