GLOSSARY

Illuminance

The amount of direct light falling on a horizontal surface called Horizontal Illuminance. Illuminance falling on a vertical surface or imaginary vertical plane is called Vertical Illuminance. The Imperial measure of Illuminance is footcandles (FC), which is Lumens per square foot. The metric measure of illuminance is Lux (Lx), which is lumens per square meter. One footcandle equals 10.56 Lux or approximately a 1:10 (FC:Lx) conversion.

THE LIGHT THAT LANDS ON THE FLOOR fc illuminance is measured at the surface, in footcandles (or lux)
Illuminance is the amount of light actually reaching a surface, measured in footcandles or lux at the floor, not the brightness of the fixture. Even coverage matters as much as the average: it is the dark gaps between pools, not the headline number, that make a deck feel unsafe. Illustrative.