Orders of magnitude (illuminance)

As visual perception varies logarithmically, it is helpful to have an appreciation of both illuminance and luminance by orders of magnitude.

Illuminance

To help compare different orders of magnitude, the following list describes various source in lux, which is a lumen per square metre.

Factor (lux)	Multiple	Value	Item
0	0 lux	0 lux	Absolute darkness
10−4	100 microlux	100 microlux	Starlight overcast moonless night sky [1]
		140 microlux	Venus at brightest [1]
		200 microlux	Starlight clear moonless night sky excluding airglow [1]
10−3	1 millilux	2 millilux	Starlight clear moonless night sky including airglow [1]
10−2	1 centilux	1 centilux	Quarter Moon
10−1	1 decilux	2.5 decilux	Full Moon on a clear night [1] [2] [3]
100	1 lux	< 1 lux	Extreme of darkest storm clouds, sunset or sunrise
101	1 decalux	40 lux	Fully overcast, sunset or sunrise
102	1 hectolux	< 200 lux	Extreme of darkest storm clouds, midday
		400 lux	Sunrise or sunset on a clear day (ambient illumination)
104	10 kilolux	10–25 kilolux	Typical overcast day, midday
		20 kilolux	Shade illuminated by entire clear blue sky, midday
105	100 kilolux	110 kilolux	Bright sunlight
		120 kilolux	Brightest sunlight

Luminance

This section lists examples of luminances, measured in candelas per square metre and grouped by order of magnitude.

Factor (cd/m2)	Multiple	Value	Item
10−6	μcd/m2	1 μcd/m2	Absolute threshold of vision [4]
10−5
10−4
10−3	mcd/m2	100 μcd/m2	Cloudy night sky without moon [4]
		400 μcd/m2	"Darkest sky" [5]
		1 mcd/m2	Night sky [6]
		1.4 mcd/m2	Typical photographic scene lit by full moon [7]
10−2		5 mcd/m2	Approximate scotopic/mesopic threshold [8]
10−1
100	cd/m2	2 cd/m2	Floodlit buildings, monuments, and fountains [9]
101		5 cd/m2	Approximate mesopic/photopic threshold [8]
		25 cd/m2	Typical photographic scene at sunrise or sunset [7]
		30 cd/m2	Green electroluminescent source [5]
102		55 cd/m2	Standard SMPTE cinema screen luminance [10]
		80 cd/m2	Monitor white in the sRGB reference viewing environment
		250 cd/m2	Peak luminance of a typical LCD monitor [11] [12]
		700 cd/m2	Typical photographic scene on overcast day [7] [9] [12]
103	kcd/m2	1 kcd/m2	Cloudy sky at noon [4] [12]
		2 kcd/m2	Average cloudy sky [5] [12]
		2.5 kcd/m2	Moon surface [5] [6]
		3–5 kcd/m2	Clear sky [6] [12]
104		5 kcd/m2	Typical photographic scene in full sunlight [7] [9]
		8 kcd/m2	Average clear sky [5] [12]
		10 kcd/m2	Clear sky at noon [4] [12]
		10 kcd/m2	White illuminated cloud [6]
		12 kcd/m2	Fluorescent lamp [5] [6]
105		75 kcd/m2	Low pressure sodium-vapor lamp [6]
		130 kcd/m2	Frosted incandescent light bulb [5] [6] [12]
106	Mcd/m2	600 kcd/m2	Solar disk at horizon [5]
107		7 Mcd/m2	Filament of a clear incandescent lamp [13]
108		100 Mcd/m2	Possible retinal damage [4]
109	Gcd/m2	1.6 Gcd/m2	Solar disk at noon [5] [6]

See also

• Photometry (optics)
• Extraterrestrial sky

Notes and references

1. Paul Schlyter, Radiometry and photometry in astronomy FAQ (2006)
2. "Petzl reference system for lighting performance". Archived from the original on 2008-06-20. Retrieved 2007-04-24.
3. Kyba, Christopher C M; Mohar, Andrej; Posch, Thomas (2017-02-01). "How bright is moonlight?". Astronomy & Geophysics. 58 (1): 1.31 –1.32. doi:10.1093/astrogeo/atx025.
4. Hahn, Lance (1996). "Photometric Units". University of Pennsylvania Medical Center, Department of Neuroscience. Retina Reference. Robert G. Smith. Archived from the original on 2019-04-21. Retrieved 2013-10-10. (see http://retina.anatomy.upenn.edu/~rob/lance/articles.html for the references within) ^{[ dead link ]}
5. Mischler, Georg. "Lighting Design Glossary – Luminance". schorsch.com. Retrieved 2013-10-10.
6. "Lighting Application". NVC Lighting Technology Corporation. Archived from the original on 2012-05-19. Retrieved 2013-10-10.
7. based on Orders of magnitude (illuminance), assuming a typical photographic scene has the same reflectance as an 18% gray card
8. Halonen, Liisa; Bizjak, Grega. "CIE Mesopic photometry – implementation for outdoor lighting" (PDF). University of Ljubljana, Faculty of Electrical Engineering, laboratory of Lighting and Photometry. Retrieved 2013-10-10.
9. based on this table of exposure values, assuming a reflected-light meter calibration constant of 12.5 cd·s/m²
10. "Screen Luminance Data Sheet" (PDF). Harkness Screens International. Archived from the original (PDF) on 2012-02-27. Retrieved 2013-10-10.
11. "Brightness and Contrast Ratio". Screen Tek. Archived from the original on 2013-08-26. Retrieved 2013-10-10.
12. When sources quote wide ranges of possible values, a (rounded) geometric mean of those values is reported here.^{[ why? ]} The luminance of the sky in particular, varies by location, season, weather, time of day and part of the sky. The sky near the horizon is often about half as bright as at zenith, which in turn is often about half as bright as the sky near the Sun. Dr. Andrew J. Marsh has created an interactive web application that can be used to visualise different sky conditions.
13. "Basics of light and lighting" (PDF). Philips Lighting Academy. 2008. p. 29. Archived from the original (PDF) on 2013-10-19. Retrieved 2013-10-18.