The Light Loss Factor (LLF) is a correction factor that accounts for the loss of light output over the life of a lighting system . This loss can be caused by lamp aging, fixture contamination, and environmental factors .
The LLF is used in lighting calculations to determine how much light will actually be available over time, rather than just based on the initial light output.
1. How is the Light Loss Factor calculated?
The LLF is calculated as the ratio of the final light level to the initial light output :
The LLF is always a value between 0 and 1 , where:
- 1.0 = No light loss (ideal conditions, practically unattainable).
- 0.7 - 0.9 = Typical values for well-maintained lighting.
- 0.5 or lower = Poorly maintained systems with high light losses.
2. Factors Influencing the LLF
| Factor | Influence on light loss |
|---|---|
| 🔥 Lamp Lumen Depreciation (LLD) | Lamps lose light output as they age. |
| 🏭 Luminaire Dirt Depreciation (LDD) | Dust and dirt reduce the efficiency of the fixture. |
| 💡 Light source lifespan | LEDs maintain their light output better than HID or fluorescent lamps. |
| 🌡 Ambient temperature | High or low temperatures can affect the performance of lamps. |
| 🔌 Electronic ballast | Efficiency loss due to aging of drivers or ballasts. |
📌 Proper maintenance and the right choice of fixtures and light sources can improve the LLF.
3. How is the LLF applied in lighting?
✅ In lighting design software → Such as Dialux, Relux or AGi32 for realistic calculations.
✅ For public lighting and street lighting → Take into account the aging and contamination of luminaires.
✅ In offices and industrial environments → Ensures that light levels remain sufficient throughout the lifespan.
✅ In shop and museum lighting → Crucial to prevent product visibility from decreasing.
📌 LLF is used to ensure that a lighting installation still meets the requirements after several years.
4. How can the LLF be improved?
🔹 Use LED lighting → LEDs have a lower lumen depreciation (high LLD).
🔹 Regular cleaning of fixtures → Reduces LDD and increases efficiency.
🔹 Schedule periodic lamp replacement → Prevents excessive light degradation.
🔹 Use luminaires with high IP ratings → Prevents dust and dirt accumulation in industrial and outdoor environments.
🔹 Choose high-quality electronics → Long-life ballasts and drivers ensure less power loss.
💡 In short:
The Light Loss Factor (LLF) is a correction factor that accounts for light loss due to aging, pollution, and environmental factors . It is used in lighting design to ensure that an installation continues to provide sufficient light over the long term. Through proper maintenance and the right choice of luminaires, the LLF can be optimized for maximum light output and energy efficiency .