Mercury batteries

As with a great number of cameras in the sixties and seventies, all of Konica’s mechanical SLRs (from the Auto-Reflex to the Autoreflex T4) were powered by 1,35v mercury batteries (type PX675 up to the Autoreflex T3N and PX625 for the Autoreflex TC and T4). For environmental reasons, the production of mercury batteries is illegal today in most western countries, which causes a problem for lovers of classic SLRs. There are, however, several possible solutions: 

1. To calibrate the meter to allow for the use of 1,55v silver oxide batteries (this is the most dependable solution, although it is costly as it requires the intervention of a camera technician inside the body);

2. To reduce the voltage of the silver oxide batteries with the aid of diodes (cheap method that doesn’t affect the internal integrity of the camera and can often be done at home);

3. To use 1,4v zinc-air batteries, whose voltage is very close to 1,35v (these batteries can be used as such, but they have a life of only a few months;

4. To compensate by regulating film speed sensibility (easiest method, but it isn’t certain that the different in exposure will be constant from one end of the scale to the other).

The question is explored in-depth here and here. There is a good coverage of available solutions on the site of Andreas Buhl.