The now (for environmental reasons) banned mercury cells have caused problems for a lot of (vintage) camera and exposure meter owners who are now facing inaccurate exposures. The constant output voltage (1.35 volts) of the mercury cell was used as a reference voltage and for powering the meter and surrounding electronics. Depending on the circuits in an exposure meter a constant voltage is actually necessary or not. A Pentax Spotmatic, for instance, has a ‘bridge’ measuring network and does not need an exact 1.35 volts. This camera works perfect on a 1.55 volts alkaline or 1.6 volts silver-oxide cell. When an alkaline or silver-oxide cell is used instead of a mercury cell without an adapter or other special measures, deviations of up to 4 Light Values! (Konica TC) can occur. In general a camera or exposure meter will not be damaged when a silver-oxide or alkaline cell is used instead of a mercury cell.
Note: this above text and PDF document is courtesy of F. de Gruijter, Waddinxveen, The Netherlands. email@example.com