Good morning, Arthur;
Yes, the exposure will be off; I think about one stop over exposed with a recent 1.5 vdc silver-oxide battery. There are a couple of ways to get around this. (1.) Cut your film speed rating in half when you set it on the camera meter. You will be fairly close with that. (2.) You can also use a Wien Cell, the air type used with hearing aids. These will be very close to the original 1.35 VDC rating of the old PX-625 mercury battery, but they do not last very long once you pull the tape off the cell. (3a.) You can have a camera repair technician put a Schottky Barrier Diode in series with one of the wires going to the battery holder and use the silver-oxide battery. (3b.) You can buy one of the Silver Cell Adapters (CRIS Camera type MR-9 or other) that has a Schottky Barrier Diode in it, and use it with a silver-oxide battery. With options 2 and 3, you use the standard ASA speed rating for your film, and the meter should be fairly close. Your camera techniian can check the light meter calibration and make any needed slight adjustments to your modified battery circuit or battery adapted camera.