Uhm (I know I should consult my player and manual now, but) if you mean the IRE setting, I think it's off. It would only affect the S-Video signal anyway, IMO.
Allen, having your setting in the ON position would actually drop the black levels to 0 IRE, which effectively crushes the blacks. It should not be brighter in the On position than in Off. The Off setting sets black levels at 7.5 IRE, which is the proper setting for broadcast. Perhaps it varies with movies, but working in television, settings are to be set at 7.5. I'm not even sure why there is a setting to drop it to 0.
I'm using a HDMI>DVI cable as I have a CRT HDTV with a DVI connection only. Not sure if that's affecting things. Still, everything looks fine with the black level setting "on."
ETA: Hmm, I've since set the black level back to "off" and everything looks fine. Go figure!