Luminance is the amount of light leaving a surface in a given direction, the brightness the eye actually perceives, measured in candelas per square meter.
It differs from illuminance, which is the amount of light falling on a surface, measured in lux or footcandles. Two surfaces with the same illuminance can have very different luminance: light concrete reflects much more light toward the eye than dark asphalt. Most parking lighting criteria are written in illuminance because it is easy to calculate and measure, but how bright and safe a garage feels depends heavily on luminance.
Why it matters in parking
- Light-colored or painted ceilings and walls raise luminance and make garages feel brighter and safer at the same lighting power.
- High luminance contrast, such as a bright fixture against a dark ceiling, causes glare.
- Entrances need careful luminance transitions so drivers coming from daylight can see.
The Parkonomics view
Paint is a lighting tool. A white ceiling in a parking garage can do as much for perceived brightness as an extra row of fixtures, at a fraction of the energy.
Related terms: Illuminance, Glare, Albedo, LED Lighting, Ambient Lighting