The term luminous flux is used to measure the visible light output of lamps, where light is not directional. It refers to the visible light emitted in all directions at any given moment. If a light source emits the same luminous flux in all directions, then the luminous intensity is the same in all direction, however usually a light will vary depending on the angle it’s observed from. A unit of measurement called the “Candela” (candle power) can be taken from various angles around the light to get a sense of the spread of light. This value quoted on a light is the peak intensity, usually measured directly in front of the light.