The product of factors that reduce output over time: lamp or LED lumen depreciation, luminaire dirt depreciation, room surface dirt and sometimes ballast or driver factors. Designers multiply initial calculated illuminance by it to get maintained illuminance, the value that codes and owners care about. Europe calls it the maintenance factor. Assuming 1.0 makes a new installation look perfect for a year and dim for the rest of its life.
Use a 0.85 light loss factor for the clean room, but go down to 0.7 for the warehouse with all that dust.
Also heard as
- LLF
- maintenance factor
- MF
Related terms
Illuminance
The amount of light falling on a surface per unit area, measured in lux or foot-candles.
L70
The number of operating hours until an LED product's light output falls to 70 percent of its initial value.
Lux
The metric measure of light landing on a surface: one lumen falling evenly on each square meter.
Point-by-point
A lighting calculation that predicts illuminance at each point on a grid from every luminaire's photometric data.