Formula
Unit
Examples
Applications
Luminance vs. Illuminance
Where: – ∅ is luminous flux (in lumens or lm) – A is the surface area (in square meters or m²). This formula elucidates how the amount of light energy falling onto a surface is distributed over the given area, quantifying the intensity of light that the surface receives. 1 lx = 1 lm/m² CGS system: Illuminance is measured in the unit known as phot, which is equivalent to 10,000 lux. 1 phot = 10,000 lux Another popular unit in the United States is foot-candles (fc), which are defined as one lumen per square foot. 1 fc = 1 lm/ft2 = 10.76 lux
Indoor office spaces commonly aim for illuminance levels between 300 to 500 lux to ensure comfortable working conditions without causing glare or visual discomfort. Public outdoor areas require higher illuminance, often ranging from 10 to 20 lux for pedestrian pathways and up to hundreds of lux for sports stadiums or high-traffic zones.
