Camera Aided Luminance Measurement of the Luminous Surfaces of Different Light Sources

It has been difficult using a luminance meter for lighting professionals to accurately measure the non-uniform luminance of artificial light sources. The emerging HDR photography techniques for luminance acquisition may overcome limitations of the conventional method. This pilot study looked into the quality of HDR images generated under nine types of artificial light sources, including incandescent, tungsten halogen, fluorescent T8, CFL, mercury, MH, HPS, LPS, and LED, for measuring their own luminous surfaces. After comparing field measured luminance data using Minolta LS-100 with those retrieved from the nine HDR images, error percents were fount 29.4% +/– 28.4% if averaging all pixels brighter than 500 cd/m², or 29.5% +/– 33.5% if manually retrieved using the provided square selection tool in Photosphere. Yet error percents were found much smaller as of 1.5% +/– 1.2% for luminance mapping the uniform white patch of Macbeth color checker. Thus, HDR images may be used for luminance measurement of light sources with enhanced accuracy.