The last time I played Minecraft (beta 1.7?) I had a large hall right above the bedrock layer which was illuminated by quite a lot torches. Having updated recently to release 1.0 down there the viewing distance is about 15 metres now. Standing in middle of the hall you cannot see any of its walls. As I play on my own server, I guess there is an operator command to disable that effect.
So, how can I disable that shortening of the viewing distance at the bedrock layer?