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The lux (symbol: lx) is the unit of illuminance, or luminous flux per unit area, ... The peak of the luminosity function is at 555 ...
In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI unit of luminous intensity is the candela (cd), an SI base unit.
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
The standard luminous efficiency function is normalized to a peak value of unity at 555 nm (see luminous coefficient). The value of the constant in front of the integral is usually rounded off to 683 lm/W. The small excess fractional value comes from the slight mismatch between the definition of the lumen and the peak of the luminosity function.
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 surface.
measuring about 10 lux [33] −14.20: An illumination level of 1 lux [34] [35] −12.60: full moon: seen from Earth at perihelion maximum brightness of perigee + perihelion + full Moon (~0.267 lux; mean distance value is −12.74, [17] though values are about 0.18 magnitude brighter when including the opposition effect) −12.40: Betelgeuse ...
The number of candelas or lumens from a source also depends on its spectrum, via the nominal response of the human eye as represented in the luminosity function. The difference between the units lumen and lux is that the lux takes into account the area over which the luminous flux is spread. A flux of 1,000 lumens, concentrated into an area of ...
Illuminance diagram with units and terminology. In photometry, illuminance is the total luminous flux incident on a surface, per unit area. [1] It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightness perception. [2]