Veiling Reflection Control by Candlepower Distribution

Achieving greater knowledge of veiling reflections, leading to the design of illumination systems for improving contrast rendition, has been one of the most important tasks facing the Illuminating Engineering Society. RQQ Report No. 4, "A Method of Evaluating the Visual Effectiveness of Lighting Systems," indicates the importance of visual performance losses occurring as a result of specular reflections from the written task. Knowledge of this subject has been progressing rapidly and although we were aware of the large contrast losses which occur with conventional systems of illumination, we were unable to compare various studies due to the lack of information on the effect of several important variables. Because of these unexplained variables, designers have been severely limited in their ability to engineer lighting systems to meet IES recommended levels of performance.

The authors felt that a thorough investigation of veiling reflections under controlled experimental conditions was required to determine the fundamental factors affecting task contrast. Consequently, luminaires with a range of typical candlepower distributions were investigated at task locations traversing the entire installations. In addition, a system specifically designed to overcome veiling reflections was tested.