Variability of contrast rendering factor in lighting installations

Abstract

The paper describes a series of measurements of contrast rendering factor (CRF) by two methods for a number of positions in ten different lighting installations. The ten targets used are representative of written and printed material found in offices. The results show that the major factors determining the value of CRF are the position of measurement and the specularity of the target material. The light distribution of the luminaires is relatively unimportant. These conclusions can be reached from measurements of CRF either as a ratio of relative visibilities or as a ratio of luminance contrasts.