Convert illuminance units — lux, foot-candle, phot, nox and more.
| Unit | Name | Value |
|---|---|---|
| lx | Lux | 10000 |
| fc | Foot-candle | 929.0313 |
| nx | Nox | 10000000 |
| klx | Kilolux | 10 |
| mlx | Millilux | 10000000 |
Formula: Millilux = Phot × 1e+07
Multiply any Phot value by 1e+07 to get Millilux.
Reverse: Phot = Millilux × 1.0000e-7
Common illuminance levels — factor: 1 ph = 1e+07 mlx
| Phot (ph) | Millilux (mlx) | Context |
|---|---|---|
| 1.000e-06 ph | 10 mlx | Dark night |
| 1.000e-05 ph | 100 mlx | Moonlit night |
| 0.0001 ph | 1000 mlx | Full moon |
| 0.001 ph | 1e+04 mlx | Indoor dim |
| 0.01 ph | 1e+05 mlx | Indoor bright |
| 0.05 ph | 5e+05 mlx | Office work |
| 0.1 ph | 1e+06 mlx | Studio lighting |
| 0.5 ph | 5e+06 mlx | Bright overcast |
| 1 ph | 1e+07 mlx | Operating room / bright overcast |
| 2.5 ph | 2.5e+07 mlx | Overcast daylight |
| 5 ph | 5e+07 mlx | Hazy sun |
| 10 ph | 1e+08 mlx | Bright sunlight |
| 13 ph | 1.3e+08 mlx | Tropical noon |
| 100 ph | 1.000e+09 mlx | Extreme |
| 1000 ph | 1.000e+10 mlx | Maximum |
1 ph = 1e+07 mlx.
Key references: 1 lx = 0.0929 fc. 1 fc = 10.764 lx. 1 phot = 10,000 lx.
Multiply result by 1.0000e-7 to recover the original ph 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.
The phot (ph) is the CGS unit of illuminance, equal to 10,000 lux = 1 lumen per square centimeter. It was the standard photometric unit before the adoption of SI units, defined in the CGS system in 1900.
Phots are found in pre-1960s scientific literature on optics, photography, and photometry. 1 phot = 10,000 lux = 929.03 foot-candles. Bright sunlight at ~100,000 lux = 10 phots. A well-lit operating room at 10,000 lux = 1 phot.
Interesting fact: The phot's name comes from the Greek phos (light), the same root as photograph and photon. Though obsolete in modern use, the phot appears in classic photometry texts and some specialized optical engineering references.
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.
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 ph = 1e+07 mlx. Reverse: 1 mlx = 1.0000e-7 ph.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.