Convert illuminance units — lux, foot-candle, phot, nox and more.
| Unit | Name | Value |
|---|---|---|
| lx | Lux | 0.001 |
| fc | Foot-candle | 0.00009290313 |
| ph | Phot | 1e-7 |
| nx | Nox | 1 |
| klx | Kilolux | 0.000001 |
Formula: Nox = Millilux × 1
Multiply any Millilux value by 1 to get Nox.
Reverse: Millilux = Nox × 1
Common illuminance levels — factor: 1 mlx = 1 nx
| Millilux (mlx) | Nox (nx) | Context |
|---|---|---|
| 0.1 mlx | 0.1 nx | Moonless overcast |
| 1 mlx | 1 nx | Dark countryside |
| 10 mlx | 10 nx | Moonlit night |
| 100 mlx | 100 nx | Full moon |
| 1000 mlx | 1000 nx | 1 lx — full moon bright |
| 1e+04 mlx | 1e+04 nx | 10 lx — candle |
| 1e+05 mlx | 1e+05 nx | 100 lx — corridor |
| 5e+05 mlx | 5e+05 nx | 500 lx office |
| 1e+06 mlx | 1e+06 nx | 1,000 lx studio |
| 5e+06 mlx | 5e+06 nx | 5,000 lx overcast |
| 1e+07 mlx | 1e+07 nx | 10 klx SAD lamp |
| 5e+07 mlx | 5e+07 nx | 50 klx hazy sun |
| 1e+08 mlx | 1e+08 nx | 100 klx bright sun |
| 1.000e+09 mlx | 1.000e+09 nx | Very bright |
| 1.300e+11 mlx | 1.300e+11 nx | Tropical sun |
1 mlx = 1 nx.
Key references: 1 lx = 0.0929 fc. 1 fc = 10.764 lx. 1 phot = 10,000 lx.
Multiply result by 1 to recover the original mlx value.
Specifies illuminance levels in lux (metric) or foot-candles (US) for architectural, retail, and workplace lighting per IES and EN 12464 standards.
Measures scene illuminance in lux with a light meter to set correct exposure for available-light photography.
Verifies that workplace lighting meets minimum requirements (typically 500 lx for offices, 300 lx for corridors) per local regulations.
Monitors grow-light illuminance in klx to optimize plant growth — fruiting plants typically need 20–60 klx.
Prescribes and measures light therapy intensity in lux for SAD treatment (10,000 lx standard) and circadian rhythm research.
Measures ambient light in lux to set appropriate display backlight levels for consistent image quality.
Millilux (mlx) equals 0.001 lux and is used for measuring very low light levels in astronomical, military, and low-light imaging applications. Starlight provides about 0.001–0.01 lx (1–10 mlx); a quarter moon about 0.1 lx (100 mlx).
Night vision equipment, wildlife cameras, and low-light sensor testing use millilux. Military specification MIL-STD-1783 specifies cockpit illumination in millilux for night-vision-compatible conditions. Astronomical photometry measures sky background in millilux.
Interesting fact: The minimum illuminance for the human eye to detect is approximately 0.0001 mlx (0.1 μlx), achieved only in the darkest conditions with fully dark-adapted eyes. Rod photoreceptors, responsible for night vision, are about 1,000 times more sensitive than cones.
The nox (nx) is an obsolete unit of illuminance equal to 0.001 lux = 1 millilux, proposed for measuring very low light levels in dim conditions. It was never widely adopted and is not recognized by any current standards body.
The nox was briefly proposed in some mid-20th century photometry literature specifically for mesopic and scotopic (low-light) illuminance measurements where lux values would be very small fractions. It never entered widespread use.
Interesting fact: The nox is one of the rarest photometric units — it rarely appears even in specialty lighting engineering texts. Its value equals exactly 1 millilux, making it redundant once millilux became the preferred notation for low illuminance levels.
Illuminance measures light falling on a surface. The SI unit is lux (lm/m²); the US standard is foot-candles (lm/ft²). Key reference levels: moonless night ~0.001 lx, full moon ~1 lx, office work 500 lx, SAD therapy 10,000 lx, bright sunlight 100,000 lx.
Exact factor: 1 mlx = 1 nx. Reverse: 1 nx = 1 mlx.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.