The National Bureau of Standards and the IES (Illuminating Engineering Society) use Candela Effective or Effective Candlepower (ECP) in specifying intensities of a flashing light source. This rating is the most meaningful when it becomes necessary to predict the visible range of flashing warning lights versus steady burning light sources.

Peak Candela or Peak Candlepower is defined asĀ the maximum light intensity generated by a flashing light during its light pulse. This is NOT a measurement of visible light, and therefore indicates nothing about how bright the light appears to the human eye.