Know your Lux from your Lumens

Decoding the terminology used to measure light levels, or illumination, can be a daunting and confusing task for those unsure of the vocabulary used. It’s important to stress straight away that we are not talking about quantities of radiant flux here, such as watts; nor are we mentioning radiant energy, measured in joules. These units of power are used to determine radiometry levels, referring to the measurement of light levels at all wavelengths, which aren’t always relevant to humanly perceptible light levels.