A Reassessment of General Lighting Practice Based on the MRSE Concept

A case is made for reassessment of the purpose of general lighting practice, involving a change from lighting standards specifying illuminance for high levels of visual performance, to providing for predictable assessments of surrounding brightness. Mean room surface exitance (MRSE) is proposed as a suitable metric for this purpose. This metric actually serves a dual role, in that apart from providing practitioners with the means to design for chosen levels of surrounding brightness, it would enable regulators to specify for perceived adequacy of illumination, PAI. The adoption of PAI specified in terms of MRSE as the prime criterion for specifying indoor illumination levels in lighting standards would invoke fundamental changes in general lighting practice. These are discussed, together with limitations of the MRSE concept and the need for both further research and feedback from industry professionals.