Pendant lights with direct distribution can be used to illuminate specific work areas, while recessed lights with a spread distribution pattern can provide general ambient lighting throughout the entire space. Another important factor is the desired ambiance you want. The Illuminating Engineering Society of North America (IESNA) has a classification system for light distribution types that describes how light spreads out on a horizontal plane. We provide the necessary knowledge on this page. Light distribution curves specify in what direction and with what intensity a luminaire emits light. Imagine stepping into a brightly lit room, yet struggling to read due to harsh glare.