Definition - What does Lux (lx) mean?
Lux (lx) is a measurement of luminescence. It is the International System of Units (SI). Lux is used in describing the total luminous that is located on a surface. It is the measurement and term described in photometry.
Lux is lumens that are measured per square meter. This accounts for the brightness of a light. Lux does not take into consideration the area but only the light’s brightness. A flashlight's beam of light is measured in lux. A flashlight with a high lux has a brighter beam of light than a flashlight with a low lux rating.
MaximumYield explains Lux (lx)
Lux is often referred to as the light's intensity. For instance, it is used to measure the brightness of the beam of light emitted from a lighthouse, searchlight, or flashlight.
When the beam of light is focused on one small area, it is bright, but when the beam spreads out over an expansive area, it lessens in intensity. This is known as the inverse square law, where the intensity is inversely proportional to the square of the distance from the source of light.
A device can emit the same amount of light but if it is spread out then it is dim but if the beam is concentrated it is brighter. This is the lux of the light. If a light has a high lux output then it is typically much brighter far away. Lux light measurements are typically used by plant growers to determine the amount of sunlight a plant requires.
Plants that require full sunlight to grow usually need 25,000 to 50,000 lux grow lights when grown in a grow room to effectively replicate the sun's light intensity. Other ways to measure grow light strength or intensity are PAR, PPF, and nanometers.