Table 2.
Photopic illuminance to achieve 50% melatonin suppression. Several practical light sources with the required photopic illuminance (lux, or lm/m2) levels at the eye, having a fixed pupil diameter of 2.3 mm, for 50% nocturnal melatonin suppression after one hour exposure (adapted from [66]). Although the absolute numbers will vary depending on pupil area, duration of exposure, exact spectral power distribution of the light source, distance from the source, the numbers in Table 2 can be used to determine the relative effectiveness of these different light sources as it may impact acute melatonin suppression, one marker of the biological clock. Whether or not these values are the same for estimating phase shifting of the timing of the biological clock by these light sources is still not established.
| Light Source | Illuminance (lux) |
|---|---|
| 2700 K compact fluorescent (Greenlite15WELS-M) | 1220 |
| 2856 K incandescent A lamp | 820 |
| 3350 K linear fluorescent (GE F32T8 SP35) | 1180 |
| 4100 K linear fluorescent (GE F32T8 SP41) | 1070 |
| 5200 K LED phosphor white (Luxeon Star) | 430 |
| 6220 K linear fluorescent (Philips Colortone 75) | 550 |
| 8000 K fluorescent (OSRAM Sylvania Lumilux Skywhite) | 610 |
| Blue LED (Luxeon Rebel, λmax = 470 nm) | 50 |
| Daylight (CIE D65) | 525 |