Convert lux, foot-candles, phot, and nox for lighting design and photography.
Illuminance Converter translates a single illuminance value among lux (lx), foot-candles (fc), phot, and nox. Enter a number in one unit and read the equivalent quantities in the others. These units all describe luminous flux incident per unit area, so conversion changes the numerical scale, not the lighting condition. The common surprise is the lux-to-foot-candle factor: because the denominator is area, the foot-to-metre relationship is squared, giving about 10.7639 lux per foot-candle.
A concrete input and expected output from the current implementation.
Input
1 lux
Expected output
1 lux = 0.09290304 foot-candles = 0.0001 phot = 1,000 nox
A lux is one lumen per square metre. Since 1 square foot is exactly 0.09290304 square metre, 1 lux equals 0.09290304 foot-candles; the definitions of phot and nox give 0.0001 phot and 1,000 nox respectively.
Lux is luminous flux per square metre, a foot-candle is luminous flux per square foot, and a phot is luminous flux per square centimetre. A nox is one millilux. On a common lux scale, 1 foot-candle equals 10.7639104167 lux, 1 phot equals 10,000 lux, and 1 nox equals 0.001 lux. Reverse conversions use the reciprocal ratios.
Each result represents the same illuminance in a different unit; the conversion does not model a lamp or scene. Large differences in the displayed numbers are expected because the unit areas differ greatly. Scientific notation can be helpful at the phot and nox ends of the scale, and a rounded display may omit digits without changing the underlying unit relationship.
A foot-candle is based on one lumen over one square foot, while lux uses one square metre. A metre is about 3.28084 feet, but illuminance is measured per area, so that length factor is squared. Consequently, 1 foot-candle is about 10.7639 lux, not about 3.28084 lux.
Not by itself. Lux describes illumination incident on a surface, while a camera setting also depends on scene reflectance, aperture, shutter time, ISO setting, and the meter's interpretation. Conversion helps when a meter and a lighting specification use different illuminance units, but it does not produce an exposure value or guarantee the same image brightness.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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