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 of lux, which is measured in lumens per square metre.

Factor
(lux)		 Multiple Value Item
0 0 lux 0 lux Absolute darkness
10−4 100 microlux 100 microluxStarlight overcast moonless night sky[1]
140 microluxVenus at brightest[1]
200 microluxStarlight clear moonless night sky excluding airglow[1]
10−31 millilux2 milliluxStarlight clear moonless night sky including airglow[1]
10−21 centilux1 centiluxQuarter Moon
10−11 decilux2.5 deciluxFull Moon on a clear night[1][2]
100 1 lux< 1 luxExtreme of darkest storm clouds, sunset or sunrise
1011 decalux40 luxFully overcast, sunset or sunrise
102 1 hectolux< 200 luxExtreme of darkest storm clouds, midday
400 luxSunrise or sunset on a clear day (ambient illumination)
104 10 kilolux10–25 kiloluxTypical overcast day, midday
20 kiloluxShade illuminated by entire clear blue sky, midday
105 100 kilolux 110 kiloluxBright sunlight
120 kiloluxBrightest 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
10−6µcd/m2 1 µcd/m2Absolute threshold of vision[3]
10−5
10−4
10−3 mcd/m2 400 µcd/m2Darkest sky[4]
1 mcd/m2Night sky[5]
1.4 mcd/m2Typical photographic scene lit by full moon[6]
10−2 5 mcd/m2Approximate scotopic/mesopic threshold[7]
10−1
100cd/m2 2 cd/m2Floodlit buildings, monuments, and fountains[8]
101 5 cd/m2Approximate mesopic/photopic threshold[7]
25 cd/m2Typical photographic scene at sunrise or sunset[6]
30 cd/m2Green electroluminescent source[4]
102 55 cd/m2Standard SMPTE cinema screen luminance[9]
80 cd/m2Monitor white in the sRGB reference viewing environment
250 cd/m2Peak luminance of a typical LCD monitor[10][11]
103 kcd/m2 700 cd/m2Typical photographic scene on overcast day[6][8][11]
2 kcd/m2Average cloudy sky[4]
2.5 kcd/m2Moon surface[4][5]
104 5 kcd/m2Typical photographic scene in full sunlight[6][8]
7 kcd/m2Average clear sky[3][4][5][11]
10 kcd/m2White illuminated cloud[5]
12 kcd/m2Fluorescent lamp[4][5]
105 75 kcd/m2Low pressure sodium-vapor lamp[5]
130 kcd/m2Frosted incandescent light bulb[4][5][11]
106Mcd/m2 600 kcd/m2Solar disk at horizon[4]
107 7 Mcd/m2Filament of a clear incandescent lamp[12]
108 100 Mcd/m2Possible retinal damage[3]
109Gcd/m2 1.6 Gcd/m2Solar disk at noon[4][5]

See also

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. Hahn, Lance (1996). "Photometric Units". University of Pennsylvania Medical Center, Department of Neuroscience. Retina Reference. Robert G. Smith. Retrieved 2013-10-10. (see http://retina.anatomy.upenn.edu/~rob/lance/articles.html for the references within)
  4. Mischler, Georg. "Lighting Design Glossary – Luminance". schorsch.com. Retrieved 2013-10-10.
  5. "Lighting Application". NVC Lighting Technology Corporation. Archived from the original on 2012-05-19. Retrieved 2013-10-10.
  6. based on Orders of magnitude (illuminance), assuming a typical photographic scene has the same reflectance as an 18% gray card
  7. 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.
  8. based on this table of exposure values, assuming a reflected-light meter calibration constant of 12.5 cd·s/m2
  9. "Screen Luminance Data Sheet" (PDF). Harkness Screens International. Archived from the original (PDF) on 2012-02-27. Retrieved 2013-10-10.
  10. "Brightness and Contrast Ratio". Screen Tek. Archived from the original on 2013-08-26. Retrieved 2013-10-10.
  11. When sources quote wide ranges of possible values, a (rounded) geometric mean of those values is reported here. 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.
  12. "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.
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