Is there any good reason why you dont want to use the noise reduction? My understanding is that it removes noise generated by long exposures by taking another image with the shutter closed, and then compares it to the first exposure.
That's dark frame subtraction you're talking about. It's used to remove hot pixels. And it increases noise, not reduces it (unless you think of hot pixels as noise, in which case you trade one type of noise for another). Unless of course Olympus does something more than simple DFS.
Ideally, you'd want to perform DFS with a master dark frame that's a result of stacking multiple dark frames, thus isolating the thing you want to remove, without adding any noise. But as far as I'm aware, this is not supported by any RAW developer.
