Question 1

Why do we have both foot-candles and lux?

Accepted Answer

Foot-candles are imperial (1 lumen/sq ft), lux are metric (1 lumen/sq m). 1 foot-candle = 10.764 lux. US uses foot-candles; most of world uses lux.

Question 2

What are recommended light levels?

Accepted Answer

Office work: 300-500 lux. Detailed tasks: 500-1000 lux. Reading: 300 lux. Hallways: 50-100 lux. Operating theater: 10,000+ lux.

Question 3

What's the difference between lumens and lux?

Accepted Answer

Lumens measure total light output from a source. Lux measures light arriving at a surface. Same lumens in a smaller area = higher lux.

Question 4

How do I convert old wattage to lumens?

Accepted Answer

Roughly: 40W incandescent ≈ 450 lumens, 60W ≈ 800 lumens, 100W ≈ 1600 lumens. LED equivalents use 80-90% less power for same lumens.

fc to lx Converter

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