I just tested a Thomas Duplex safelight with the color filters installed. It has a new bulb, new B&W FBD filters in the base, and new FCD filters in the vanes with the vanes fully closed like the instructions say, and even with 5 minutes exposure it does not fog the paper from 4 feet away. The safelight is bright enough to barely see the opposite side of the darkroom which is 12-14 feet away. I can easily see any trays or boxes in there. Since this is in a school environment, and the darkroom is for B&W mostly, both classes can work in the same room at the same time with some level of visibility.