Started an overnight render and watched it go through the first couple of passes, just to make sure I didn't miss anything obvious during scene construction, and then walked away, satisfied that the lighting etc was what I was looking for. It was just a test render, so I wasn't too concerned about it. But, come morning, I find that the picture has rendered out so dark I can't even make out what it is supposed to be! How is this possible? None of the light settings have changed, but more importantly, why would it suddenly turn dark somewhere in the middle of a render? This has happened two nights in a row now on the scene I am working on. Fixing it involved cranking the intensity of the light (I'm using a single radial, no falloff, intensity of 3, plaus a volumetric spot), then slowly lowering the brightness back to where it was originally. This scene is just about ready for final rendering, so I'd like not to have to this happen again. Has this happened to anyone else, or any ideas to stop it from happeneing again?