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1 lux < 1 lux: Extreme of darkest storm clouds, sunset or sunrise 10 1: 1 decalux: 40 lux: Fully overcast, sunset or sunrise 10 2: 1 hectolux < 200 lux: Extreme of darkest storm clouds, midday 400 lux: Sunrise or sunset on a clear day (ambient illumination) 10 4: 10 kilolux: 10–25 kilolux: Typical overcast day, midday 20 kilolux
In SI units illuminance is measured in lux (lx), or equivalently in lumens per square metre (lm·m −2). [2] Luminous exitance is measured in lm·m −2 only, not lux. [4] In the CGS system, the unit of illuminance is the phot, which is equal to 10 000 lux. The foot-candle is a non-metric unit of illuminance that is used in photography. [5]
The lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, in the International System of Units (SI). [ 1 ] [ 2 ] It is equal to one lumen per square metre. In photometry , this is used as a measure of the irradiance , as perceived by the spectrally unequally responding human eye, of light that hits or passes through a ...
The distance between the center and this point is defined as L1. The similarly measured distance in the direction away from the light is L2. The depth of illumination without needing to refocus is the sum of the two distances L1 and L2. In the second edition of the IEC standard, published in 2009, the threshold value was revised from 20% to 60% ...
In the US lighting industry, foot-candles are a common unit of measurement used by architects to calculate adequate lighting levels. Foot-candles are also commonly used in the museum and gallery fields in the US, where lighting levels must be carefully controlled to conserve light-sensitive objects such as prints, photographs, and paintings, the colors of which fade when exposed to bright ...
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A tea light-type candle, imaged with a luminance camera; false colors indicate luminance levels per the bar on the right (cd/m 2). Luminance is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. [1]
The design day for daylight factor calculations is based on the standard CIE overcast Sky for 21 September at 12:00pm, and where the Ground Ambient light level is 11921 Lux. CIE being the Commission Internationale de l´Eclairage, or International Commission on Illumination.