Measurements and Calculations – Illuminating Engineering Society

M/P ratios – Can we agree on how to calculate them?

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].

Focusing on Daylight Spectra

By Mehlika Inanici, Ph.D.

The dynamic intensity and spectra of daylight inform human beings about the passage of time and weather, produce the best color rendition, regulate circadian rhythms in all living beings, and facilitate sustainable lighting practices.

Simplifying Melanopsin Metrology

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.

An Intuitive Metric for Lumen Maintenance

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.

The Lighting Design Objectives (LiDOs) Procedure

By Christopher Cuttle, MA, PhD, FCIBSE, FIESANZ, FIESNA, FSLL

This procedure is based on the concept that there is real advantage to be gained from changing the illumination metrics used for specifying, measuring and predicting lighting applications so that they relate to people’s responses to visible effects of lighting in indoor applications.