Pilot Study on Measurement of Luminance Distribution in LED Floodlights

LED lighting technology has been advancing quite rapidly. The luminance distribution in LED floodlights is assumed to dif fer from that of high-intensity discharge (HID) floodlights. However, measuring the luminance of LED floodlights is difficult because of their high luminance and narrow beam. The purpose of this study was to clarify the problems with the luminance measurement of floodlights using digital cameras. The modulation transfer function (MTF) characteristics of seven different camera systems were obtained, and the lumi nance distribution of different types of LED floodlights was measured using four different camera systems. The luminance distribution of the LED floodlights measured using by the camera systems with different MTFs showed different values of luminance. The results show that a higher resolution does not necessarily mean a better MTF is maintained. Identifying the MTF characteristics of the camera system is important to determine the accuracy of the luminance distribution measured with the system.