What is the difference between luminance vs. illuminance?
When talking about light and lighting design; two of the most confusing and often misused terms are luminance and illuminance. They are often substituted for one another, interchanged and used incorrectly by people. The Fusion Optix BrightMinds® camera app measures luminance. Here’s a brief explanation of the two terms.
Luminance
Luminance is the density of luminous intensity in a given direction and falls within a given solid angle. It is measured in cd/m2 or nits.
Luminance is often used to characterize the emission from a diffuse surface. It indicates how much luminous power will be perceived by eye when viewing the surface from a particular angle. Luminance remains the same regardless of the distance from the light source.
Illuminance
Illuminance is the density of photons which fall within a given surface area. It is measured in lux, or footcandle(fc).
Illuminance can be measured with a lux meter. For a given light source, the closer to a light source the illuminated area is, the higher the Illuminance value.
Illuminance is used in lighting applications to measure the amount of light reaching an object such as a wall.
The sky is illuminance whereas the light reflected of the causeway in the foreground is luminance
