Typical Causes of Errors During Measuring Luminance Distributions in Relation to Glare Calculations

The number of high luminance light sources commonly used in lighting technology is systematically growing, causing an increase in number of potential problems. One of them is the problem of discomfort glare and ways to measure it. Both calculation and measurement methods connected with this parameter have a series of disadvantages and advantages. Among the serious disadvantages, there can be dominant digital “models” of light sources and luminaires, which do not include, practically, any direct information on luminance distribution. To make the measurement results correspond to the calculation results, computer simulations and visual impression of the people assessing the lighting, the measuring devices should correctly record the analyzed parameters. The accurate parameters recording means the situation under which the measurement result is possibly close to what the human eye records. The modern measurement systems, among which there are undoubtedly ILMDs - Imaging luminance measuring devices, are potentially ideal to record all parameters used to calculate glare. Research done by the author proves that especially as far as the small light sources are concerned, such as LEDs and multi-source luminaire systems the parameters of the equipment used have a big influence on the measurement results. Especially, an angular field of view of single pixel of the digital sensor, which relates to a CCD or CMOS sensor size, dimensions of single photo-cell, focal length and technology that is used to make this device (B/W, color). A problem of the influence of depth of field of digital recording equipment with respect to the measured luminance values was dealt with. In this paper and presentation, the relationships of ILMD parameters, such as a field of view of a given type of sensor and single photo-element, including the used lens, will be presented.