What is the Beam Spread?
The beam angle is the angle across the cone of light from one beam edge to the opposite beam edge. The beam edge is the cone-shaped surface where the beam intensity is 50% of what it is at the center of the beam. (50% is somewhat arbitrary, but seems to be the most commonly used figure.) A flood light has a beam spread of around 22 degrees or more. A spot has a beam spread of less than 21 degrees. (21° is also arbitrary, but commonly used as the dividing point between floods and spots.) If you compare a flood and spot with the same light elements (and lumen output,) the flood has a lower â brightness,â as defined by Center Beam Candle Power (luminance) because the bulb is spreading the light over a larger cone. That may not seem entirely fair to the flood light, but research has linked human perception of â brightnessâ with luminance, so using CBCP is valid. And converting CBCP to Watt-equivalents using a constant ratio is also valid for our purposes. It is interesting to note that wh
