The Illuminating Engineering Society of North America (IESNA) established illuminance categories. These seven categories are based on descriptions of various visual tasks:
|
Category |
Space |
Illuminance |
|
| Orientation and simple visual tasks |
A |
Public spaces |
30 lux (3 footcandle) |
| B | Simple orientation for short visits |
50 lux (5 footcandle) |
|
| C | Working spaces where simple visual tasks are performed |
100 lux (10 footcandle) |
|
| Common visual tasks | D | Performance of visual tasks of high contrast and large size |
300 lux (30 footcandle) |
| E | Performance of visual tasks of high contrast and small size, or visual tasks of low contrast and large size |
500 lux (50 footcandle) |
|
| F | Performance of visual tasks of low contrast and small size |
1000 lux (100 footcandle) |
|
| Special visual tasks | G | Performance of visual tasks near threshold |
3,000 to 10,000 lux (300 to 1000 footcandles) |