Photometry is the measurement of visible light as perceived by the human eye. Photometry is a name formed by combining the words photo and metry. Photo is a prefix meaning light. Metry refers to the process of measurement.
Light measuring devices called lux meters can measure with high precision in a wide measuring range. But when it comes to LEDs things get a little more complicated. Different brands and models of lux meters may take different measurements at the same point.
Illuminance or light level is the total amount of light per unit area on a surface. Its unit is lux and is used in abbreviated form as lx. How much an environment is lighted-up expressed by the value of lux. It can be said that the higher the value of...