LED & Solid State Lighting

How do you measure the naturalness of light?

Bridgelux proposes metric relating LED output to natural light


LED manufacturer Bridgelux has announced a quality-of-light metric for white LEDs, or even solid-state lighting (SSL) end products, called Average Spectral Difference (ASD) that is intended to provide a simple way for product developers, lighting designers/specifiers, and other lighting professionals to easily understand how the output of an LED compares to so-called “natural light.” ASD is based on details in the spectral power distribution (SPD) of an LED and how that SPD compares with the SPD of a reference illuminant that’s considered representative of natural light. ASD is expressed as a percentage with 0% representing performance equivalent to the natural reference.