2-DIMENSIONAL PHOTOMETRY FOR INTERIOR SURROUND LIGHTING

Photopic photometry is often found to be limited when applied to inter ior lighting applications. Some of these limitations arise from the la rge field-of-view which is typical of most lighting conditions, as wel l as from the various consequences of the scotopic sensitivity of the eye. We present here a new graphing procedure which makes these limita tions readily apparent and provides a clear visual means to make predi ctions that can be tested in lighting practice or experimental laborat ories. This graphing method is intended to be used to compare lamps, t he comparison being with respect to multiple variables: (1) disability glare, (2) visual effort, (3) room brightness, and (4) relative energ y cost. To provide these four output measures, the graphing method use s two independent photometric parameters as inputs: vertical photopic illuminance and vertical scotopic illuminance. Hence, the photometric parameters important for interior surround lighting applications are t wo-dimensional. Lamp efficacy is an additional constant input paramete r for each lamp. This paper describes the relevant variables, the way to graphically interpret the measures, examples in the use of the grap hs, and the limitations of the method.