Understanding Illuminance (Lighting Intensity)
Illuminance quantifies light falling onto a given surface. As light spreads outward from a source, illuminance decreases according to the inverse-square law.
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Illuminance Converter
Convert light illuminance units including lux, foot-candles, phots, and lumens per square meter.
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0.9290304 Foot-candle
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Educational Guide
Real-World Illuminance Examples
Direct noon sunlight is ~100,000 lux, an overcast day is ~1,000 lux, a well-lit office is ~500 lux, and full moonlight is ~0.1 to 0.25 lux.
Architectural & Photography Standards
Architects design commercial lighting using foot-candles (US) or lux (Europe/SI) to comply with workplace safety codes, energy regulations, and visual ergonomics.
Photometry Measurement Units
The SI standard is the Lux (lumen/m²). The historical CGS unit is the Phot (lumen/cm² = 10,000 lux), and the imperial standard is the Foot-candle (lumen/ft²).
Frequently Asked Questions
What is illuminance?
Illuminance is the total luminous flux (light energy) incident on a surface per unit area. It measures how brightly lit a surface appears.
How do I convert Foot-candles to Lux?
Multiply the Foot-candle value by 10.764 to obtain Lux. For quick mental estimation, 1 foot-candle is approximately equal to 10 lux.
What is recommended indoor lighting in Lux?
Standard living rooms need ~150-300 lux, office desks and classrooms require ~500 lux, and precision assembly/drafting tasks need 1,000-2,000 lux.
What is the difference between Lumens and Lux?
Lumens measure total light emitted by a light source in all directions, whereas Lux measures how much of that light actually hits a specific surface area (1 Lux = 1 Lumen/m²).
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