Measure of Light


The chapel of Notre Dame du Haut in Ronchamp, France

Light is an important factor to be considered during architectural design. We use illuminance to refer to the intensity of light that shine upon a certain area. There are two units to present the illuminance.

ILLUMINANCE: (old term: ILLUMINATION) Definition: Density of luminous flux on a surface

Symbol: E; Unit: Footcandle (fc) = (1 lumen per sq. foot); Lux (lx) = (1 lumen per sq. meter)

Conversions: FC = Lux x .0929; LUX = FC x 10.76 – (ie: 50 FC = 538 LUX)

The illuminating Engineering Society sorted different tasks performed in buildings into 1 to 9 categories. Each task were assigned with recommended amount of lux/footcandles. When design the lighting of a building or room, the architect should consider these categories and decide how much degree of iluminance is appropriate for the performances appear in it.


“Footcandles and Lux.” Footcandles and Lux. 1 Jan. 1999. Web. 8 Oct. 2014. <;.



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