I recently was given my Grandmother's OM-1 and had a question about the battery. Apparently, the original battery was Mercury based and is no longer manufactured. When I asked the folks at the local camera shop, I was told that there were several replacements availible, but they all had some effect on the light meter. However, no one could tell me what those effects were. Has anyone else run across this? If so, can you tell me exactly what the effects are? Thanks for your help!