Table 1. Examples of nighttime light sources and their approximate intensities.

Light source	Intensity (lux)	Distance	References
Overcast night sky	0.00003–0.0001	At surface of Earth	Gaston et al.8
Clear starry night	0.001	At surface of Earth	Gaston et al.8
Full moon	0.1–0.3	At surface of Earth	Gaston et al.8
Urban sky glow	0.15	At surface of Earth	Gaston et al.8
Residential side street	5	Unknown	Gaston et al.8
Lighted parking lot	10	Unknown	Gaston et al.8
Main road street lighting	15	Unknown	Gaston et al.8
9.7 Inch tablet computer	40	10 in	Wood et al.12
Smartphone	>40 bluxa	20 cm	Oh et al.15
ICU step-down unit	1.3–47.3	Unknown	Fanfulla et al.16
24 Inch LED computer screen	~100	Unknown	van der Lely17
Intensive care unit (ICU)	190.5	Unknown	Meyer et al.,119
Most homes	100–300	Unknown	Gaston et al.8

Abbreviation: LED, light-emitting diode.

^aBlux is a weighted measure of light intensity based on circadian-responsive wavelengths.