Forum for Illumination Research, Engineering, and Science (FIRES)

By Travis Longcore

From the position of wildlife, the best artificial light at night is no artificial light at night.

By Naomi J. Miller, PNNL; Anne (Lia) Irvin, PNNL

The candela and the lumen are units based on one form of human spectral sensitivity, characterized with the weighting function known as V(λ), which was derived under a very narrow set of experimental conditions by multiple researchers, and the results awkwardly combined in 1924 to produce the familiar photopic response function [Sharpe and others, 2005].

By Sam Berman, HFIES
Senior Scientist Emeritus Lawrence Berkeley National Laboratory
and
Robert Clear, FIES
Staff Scientist (Retired) Lawrence Berkeley National Laboratory

During the past two decades, the lighting community has come to recognize that retinal photoreception extends beyond rods and cones, and includes a small number of intrinsically photosensitive retinal ganglion cells (ipRGCs) with their own unique spectral sensitivity. In this dialogue we provide a simple method for incorporating the metrological consequences of this sensitivity into lighting practice.

By Eric Bretschneider

For better or for worse, the lighting industry commonly associates the lifetime of LEDs and LED-based lighting products with L₇₀ – the amount of time for the lumen maintenance of an LED-based device to reach 70% of its initial value. Admittedly, the failure of other components, particularly those that provide power to LEDs, are more likely to determine the overall lifetime of an LED-based component or luminaire. However, only lumen maintenance is considered here.