I have an OM2n, and the meter is wrong. It says that it's dimmer than it really is, causing me to overexpose. I could adjust the film speed to compensate, but that would be confusing and I would like to fix the meter itself. Is this something that's easy to adjust? Also, how long should a set of batteries last? I'm only gettting a few months of life out of Energizer silver oxide batteries, and when they go, the camera is useless.