# 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 |
| 10$^{−4}$ | 100 microlux | 140 microlux | Venus at brightest |
| 10$^{−4}$ | 100 microlux | 200 microlux | Starlight clear moonless night sky excluding airglow |
| 10$^{−3}$ | 1 millilux | 2 millilux | Starlight clear moonless night sky including airglow |
| 10$^{−2}$ | 1 centilux | 1 centilux | Quarter Moon |
| 10$^{−1}$ | 1 decilux | 2.5 decilux | Full Moon on a clear night |
| 10$^0$ | 1 lux | < 1 lux | Extreme of darkest storm clouds, sunset or sunrise |
| 10$^1$ | 1 decalux | 40 lux | Fully overcast, sunset or sunrise |
| 10$^2$ | 1 hectolux | < 200 lux | Extreme of darkest storm clouds, midday |
| 10$^2$ | 1 hectolux | 400 lux | Sunrise or sunset on a clear day (ambient illumination) |
| 10$^4$ | 10 kilolux | 10–25 kilolux | Typical overcast day, midday |
| 10$^4$ | 10 kilolux | 20 kilolux | Shade illuminated by entire clear blue sky, midday |
| 10$^5$ | 100 kilolux | 110 kilolux | Bright sunlight |
| 10$^5$ | 100 kilolux | 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/m$^2$) | Multiple | Value | Item |
| 10$^{−6}$ | μcd/m$^2$ | 1 μcd/m$^2$ | Absolute threshold of vision |
| 10$^{−5}$ | | | |
| 10$^{−4}$ | | | |
| 10$^{−3}$ | mcd/m$^2$ | 100 μcd/m$^2$ | Cloudy night sky without moon |
| 10$^{−3}$ | mcd/m$^2$ | 400 μcd/m$^2$ | "Darkest sky" |
| 10$^{−3}$ | mcd/m$^2$ | 1 mcd/m$^2$ | Night sky |
| 10$^{−3}$ | mcd/m$^2$ | 1.4 mcd/m$^2$ | Typical photographic scene lit by full moon |
| 10$^{−2}$ | | 5 mcd/m$^2$ | Approximate scotopic/mesopic threshold |
| 10$^{−1}$ | | | |
| 10$^0$ | cd/m$^2$ | 2 cd/m$^2$ | Floodlit buildings, monuments, and fountains |
| 10$^1$ | | 5 cd/m$^2$ | Approximate mesopic/photopic threshold |
| 10$^1$ | | 25 cd/m$^2$ | Typical photographic scene at sunrise or sunset |
| 10$^1$ | | 30 cd/m$^2$ | Green electroluminescent source |
| 10$^2$ | | 55 cd/m$^2$ | Standard SMPTE cinema screen luminance |
| 10$^2$ | | 80 cd/m$^2$ | Monitor white in the sRGB reference viewing environment |
| 10$^2$ | | 250 cd/m$^2$ | Peak luminance of a typical LCD monitor |
| 10$^2$ | | 700 cd/m$^2$ | Typical photographic scene on overcast day |
| 10$^3$ | kcd/m$^2$ | 1 kcd/m$^2$ | Cloudy sky at noon |
| 10$^3$ | kcd/m$^2$ | 2 kcd/m$^2$ | Average cloudy sky |
| 10$^3$ | kcd/m$^2$ | 2.5 kcd/m$^2$ | Moon surface |
| 10$^3$ | kcd/m$^2$ | 3–5 kcd/m$^2$ | Clear sky |
| 10$^4$ | | 5 kcd/m$^2$ | Typical photographic scene in full sunlight |
| 10$^4$ | | 8 kcd/m$^2$ | Average clear sky |
| 10$^4$ | | 10 kcd/m$^2$ | Clear sky at noon |
| 10$^4$ | | 10 kcd/m$^2$ | White illuminated cloud |
| 10$^4$ | | 12 kcd/m$^2$ | Fluorescent lamp |
| 10$^5$ | | 75 kcd/m$^2$ | Low pressure sodium-vapor lamp |
| 10$^5$ | | 130 kcd/m$^2$ | Frosted incandescent light bulb |
| 10$^6$ | Mcd/m$^2$ | 600 kcd/m$^2$ | Solar disk at horizon |
| 10$^7$ | | 7 Mcd/m$^2$ | Filament of a clear incandescent lamp |
| 10$^8$ | | 100 Mcd/m$^2$ | Possible retinal damage |
| 10$^9$ | Gcd/m$^2$ | 1.6 Gcd/m$^2$ | Solar disk at noon |