What is unit of illumination?

Light intensities are usually measured in candle power. What that means is the equivalent of the light of one candle, measured at a distance of one foot, sometimes called, foot candles' or canDELLas'.

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In the SI system the flux or "amount" of light, is measured in lumen; and the illuminence or brightness of the light, on a surface in lumens per square metre, a compound unit called the lux.