That's something I read about in Gene Nocon's Darkroom Printing book. The idea being that if you took a 'normal' light meter reading at night or a dark scene like a band on a stage, the meter will do what it always does and give the correct exposure for an 18% grey scene. A night or low light scene is significantly lower than 18% brightness so less exposure is needed than the meter suggests..
Mark Barendt, Beaverton, OR
"We do not see things the way they are. We see things the way we are." Ana´s Nin