Quote Originally Posted by wiltw View Post
Nevertheless, the Olympus OM-1 is absolutely dependent upon constant 1.3v, its meter does not align two needle but is similar in appearance to the Spotmatic (align needle to center of indicator area), its needle swings out when power is off.
The fact that the needle is not centred when it's off is a sign that it is not a bridge circuit so you are correct that it needs a stable 1.3v to work accurately.

The only minor problem which can occur if using 1.5v cells in a 1.3v camera with a bridge circuit is that if you have positions marked as +/- one or two stops for exposure compensation, they will be a bit further out on the meter's swing than they were with a 1.3v cell. Not by much though.