Illuminance explained
Illuminance is the amount of light falling on a surface. One lux is one lumen spread over one square meter. The foot-candle, still used in US lighting design and photography, is one lumen per square foot, about 10.764 lux.
| Situation | Lux | Foot-candles |
|---|---|---|
| Full moon | 0.1–0.3 | 0.01–0.03 |
| Living room | 100–300 | 10–30 |
| Office desk | 300–500 | 30–50 |
| Overcast day | 1,000–10,000 | 100–1,000 |
| Direct sunlight | 30,000–100,000 | 3,000–10,000 |
Lumens measure the total light a lamp emits; lux measures how much of it reaches a surface. The same lamp gives fewer lux the farther away it is.