T&M Understanding Lux and Illuminance: A Guide to Light Levels
This article explores the concept of lux, also known as illuminance, and provides charts outlining recommended light levels for various indoor and outdoor environments. Illuminance refers to the amount of light falling on a surface, and it’s a crucial factor in creating comfortable and functional spaces.
What is Illuminance?
Illuminance, or light level, measures the total luminous flux (light) incident on a surface per unit area. Think of it as how much light is actually hitting a particular spot. It’s commonly measured in:
- Lux (lx): The standard unit in the International System of Units (SI).
- Footcandles (fc, ftcd, fcd): Often used in the United States.
Here’s how these units relate to each other:
- 1 Lux = 1 Lumen/meter²
- 1 Footcandle = 1 Lumen/sq. ft = 10.752 Lux
- 1 Lux = 0.0001 Phot = 0.0929 Footcandle
- 1 Phot = 1 Lumen/sq. cm = 10,000 Lux
Light Levels from Natural Sources
The following table illustrates the illuminance levels provided by different natural light sources:
| Natural Source | Illumination (ftcd) | Illumination (lux) |
|---|---|---|
| Sunlight | 10,000 | 107,527 |
| Full Daylight | 1,000 | 10,752 |
| Overcast Day | 100 | 1,075 |
| Very Dark Day | 10 | 107 |
| Twilight | 1 | 10.8 |
| Deep Twilight | 0.1 | 1.08 |
| Full Moon | 0.01 | 0.108 |
| Quarter Moon | 0.001 | 0.0108 |
| Starlight | 0.0001 | 0.0011 |
| Overcast Night | 0.00001 | 0.0001 |
Recommended Light Levels Indoors
This chart provides recommended illuminance levels for various indoor environments:
| Light Levels Indoors | Illumination (Lux, Lumen/sq.m ) |
|---|---|
| Public areas with dark surroundings | 20 to 50 |
| Warehouses, Homes, Theaters | 150 |
| Easy Office Work, Classes | 250 |
| Normal office work, PC work, Study library, Groceries, Labs, Show rooms | 500 |
| Super markets | 750 |
| Mechanical workshops, normal drawing work | 1000 |
| Detailed drawing work | 1500 to 2000 |
| Visual tasks with low contrast & very small size for prolonged periods of time | 2000 to 5000 |
| Training rooms | 500 |
| Auditoria | 150 to 200 |
| Child care centers, Parking , entrances, physical fitness space | 500 |
Recommended Light Levels Outdoors
The following image displays recommendations for light levels on roadways and sidewalks:
Related Resources:
For more information on lighting and measurement, check out these related topics:
- [Lux vs Lumens](link to a related article about lux vs lumens)
- [LED test equipments](link to a related article about LED test equipment)
- [Lux Light Meter](link to a related article about lux light meters)
This information should help you understand the importance of light levels and how to achieve optimal illumination in various spaces.
