The lux is the International System of Units unit for luminous emittance. It's used to measure the apparent intensity of light as it strikes a surface. The candela is the International System of Units (SI) unit for luminous intensity. It measures the apparent intensity of a light source in a specific direction.
Convert a measurement in lux (lx) to a measurement in lumen (lm). The lumen is the SI unit of luminous flux, which measures the perceived power of light. The difference between lux and lumen is that lux takes the area of luminous flux into account, whereas the lumen does not. The lux may therefore be expressed in terms of lumen per unit area. A lux is equal to 1 lumen per square meter.
Calculate a measurement in lumen to a measurement in candela (cd). The candela takes the radiation angle into account, which is measured in steradians (sr). The steradian is the SI unit for a solid angle and is equal to 1/4 pi of the entire sphere. A lumen is equal to 1 candela x steradian.
Express the lux in terms of the candela. Step 1 shows that 1 lx = 1 lm / m ^2. Step 2 shows that 1 lm = 1 cd x sr. This shows that 1 lx = 1 lm / m^2 = 1 cd x sr / m^2, so 1 lx = 1 cd x sr / square meter.
Convert lux to candela. The equation 1 lx = 1 cd x sr / square meter is equivalent to 1 cd = 1 lm x m^2 / sr. A candela is therefore equal to 1 lumen x square meter per steradian.
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