Effect of the illuminance meter used on the results of color light pollution measurements

The paper presents the results of measurements of illuminance. Twenty-two types of illuminance meter with known spectral sensitivity curves of photometric heads and eleven lamps emitting colored light were used. Laboratory measurements were conducted at a characteristic point, with a focus on assessing intrusive light, with a value of 3 lx. The considerations were supplemented with simulated illuminance calculations. For most illuminance meters, correlations were observed between the measurement results and the calculations. This allows the conclusion that, especially in the case of colored light, one of the main factors affecting the measurement result is the spectral sensitivity curve of the photometric head. The greatest discrepancies in the obtained illuminance values were found in the case of lamps emitting blue light. The paper highlights the fact that measuring low illuminance values produced by lamps emitting colored light is not an easy task. Depending on the illuminance meter used, conclusions regarding the assessment of intrusive light may vary. The aim of the paper is to indicate that not all calibrated illuminance meters are suitable for this assessment.