A reflected light meter reading measures the level of light reflected from the subject. An incident light meter reading measures the amount of light falling on the subject. The resulting exposure is an average between the light and dark tones present. When light and dark tones are of equal distribution this average light reading is suitable for exposure. When light or dark tones dominate the photographer must increase or decrease exposure.
Adapted from Studio Photography Essential Skills by John Child (Focal Press, 2008; $30)_