Originally Posted by Marc Sabatella 
True. But the problem with colored filters is that most of the situations we are talking about here involve low light levels as it is. A blue filter means it's going to be that much hard to get enough light at all. Of course, one could question whether bad light is better than no light. But I do find that if nothing else, the red channel on its own often makes a fine B&W conversion.
True enough, but we were able to do it with 400 ISO film, and since with digital, 1600 is the new 400, so we gain a couple of stops advantage.