Quality analysis of photometers using vertical window illuminance measurements

In urban areas, one of the main forms of light pollution is the intrusion of light through windows into residential buildings. This phenomenon can harm human health, so standards have been introduced to define limits for vertical illuminance. This study aims to assess the levels of outdoor lighting on the windows of residential buildings in Poland in terms of compliance with standards for protection against intrusive light, as well as to compare the results obtained using various commercially available photometers. The paper presents the results of field measurements of vertical illuminance on the window surfaces of 17 residential buildings in several cities in Poland. The measurements were made with 22 photometers representing different metrological levels. The measuring instruments selected for the study are a sample of commercially available photometers. Despite the same lighting conditions on the surface of the individual windows, discrepancies can be seen in the measured illuminance values of the different photometers. The vertical illuminance measurements were subjected to statistical analysis. It was found that of the 22 photometers, only a few were suitable for assessing obtrusive light from outdoor lighting installations. It has also been noted that on window surfaces, in buildings located on a busy street in the city centre, the illuminance can reach up to 100 lx, many times exceeding the permissible values of 1, 2, 5, 10 and 25 lx.