Equivalent Melanopic Lux (EML) is defined as...

• A. The product of visual lux and melanopic ratio
• B. The sum of visual lux and melanopic ratio
• C. The ratio of melanopic lux to visual lux
• D. The visual lux alone

Answer: (A)

Equivalent Melanopic Lux reflects how much light is both visually bright and able to stimulate the circadian system. The melanopic ratio is defined as melanopic lux divided by photopic (visual) lux, so multiplying visual lux by this ratio gives melanopic lux. In WELL practice, EML is defined as that product, which effectively equals melanopic lux. This makes EML a measure of circadian-relevant light intensity derived from the actual light level you see. The other options don’t capture this combined effect: summing would mix different scales, a ratio would remove the actual light amount, and visual lux alone ignores the circadian-biological impact.