Lighting Knowledge
What is the difference between the IES and CIE standards for beam angle?
Difference between the IES (International Illuminating Society of North America) and CIE (Commission Internationale de l’Illumination) standards for beam angle?
CIE (Commission Internationale de l’Illumination) standard is that the center (A) intensity of 50% of the area (pink area in the figure below), C-C angle, defined as the beam angle, for example, assuming that the intensity of A is 100, the pink edge of the intensity is 50
50%,CIE
IES (International Illuminating Society of North America), the center (A) intensity of 10% of the area (the green edge of the figure below), D-D angle, defined as the beam angle, as an example, assuming that the intensity of A is 100, the green edge of the intensity is 10.
10%,IES
The same called beam angle, CIE (International Commission on Illumination) and IES (International Illuminating Society of North America) are different, so be sure to confirm the local standards when purchasing.
Generally speaking, narrow beam: beam angle <20 degrees; medium beam: beam angle 20~40 degrees, wide beam: beam angle >40 degrees.
CIE and IES
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