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The same 1,000 lumens, spread out over ten square metres, produces a dimmer illuminance of only 100 lux. In equation form, 1 lx = 1 lm/m 2 . A source radiating a power of one watt of light in the color for which the eye is most efficient (a wavelength of 555 nm, in the green region of the optical spectrum) has luminous flux of 683 lumens.
400 μcd/m 2 "Darkest sky" [5] 1 mcd/m 2: Night sky [6] 1.4 mcd/m 2: Typical photographic scene lit by full moon [7] 10 −2: 5 mcd/m 2: Approximate scotopic/mesopic threshold [8] 10 −1: 10 0: cd/m 2: 2 cd/m 2: Floodlit buildings, monuments, and fountains [9] 10 1: 5 cd/m 2: Approximate mesopic/photopic threshold [8] 25 cd/m 2: Typical ...
[2] Lumen maintenance compares the amount of light produced from a light source or from a luminaire when it is brand new to the amount of light output at a specific time in the future. For instance, if a luminaire produced 1,000 lumens of light when it was brand new and now produces 700 lumens of light after 30,000 hours, then it would have ...
cd/m 2 (= lm/(sr⋅m 2)) L −2 ⋅J: Luminous flux per unit solid angle per unit projected source area. The candela per square metre is sometimes called the nit. Illuminance: E v: lux (= lumen per square metre) lx (= lm/m 2) L −2 ⋅J: Luminous flux incident on a surface Luminous exitance, luminous emittance M v: lumen per square metre lm/m ...
One lux is equal to one lumen per square metre: 1 lx = 1 lm/m 2 = 1 cd·sr/m 2. A flux of 1000 lumens, spread uniformly over an area of 1 square metre, lights up that square metre with an illuminance of 1000 lux. However, the same 1000 lumens spread out over 10 square metres produces a dimmer illuminance of only 100 lux.
A foot-candle (sometimes foot candle; abbreviated fc, lm/ft 2, or sometimes ft-c) is a non-SI unit of illuminance or light intensity. The foot-candle is defined as one lumen per square foot. This unit is commonly used in lighting layouts in parts of the world where United States customary units are used, mainly the United States. [ 1 ]
However, people still sometimes use it to describe the luminous intensity of high powered flashlights and spotlights. Narrow-beamed lights of all sorts can have very high candlepower specifications, because candlepower measures the intensity of the light on a target, rather than the total amount of light it emits.
Zodiacal light varies quite a lot in intensity depending on the position of the Earth, location of the observer, time of year, and composition and distribution of the reflecting dust. Scattered light from extraterrestrial sources