Convert between lux (lx), foot-candle (fc), lumen/square meter (lm/m²), and other illumination units with scientific precision.
The SI unit of illumination, defined as one lumen of luminous flux per square meter. 1 lux = 1 lumen/m² = 1 foot-candle ÷ 10.764. Named after the Latin word for light.
Common uses: Building lighting design, photography exposure calculations, workplace lighting standards, display brightness specifications, and international lighting measurements.
The illumination from a light source of one candle power at a distance of one foot. 1 foot-candle ≈ 10.764 lux. Still widely used in North America for lighting design and specifications.
Application: American lighting standards, architectural lighting design, workplace illumination specifications, and legacy lighting documentation.
The illumination from a one-candle light source at a distance of one meter. 1 meter-candle = 1 lux. Equivalent to the SI lux unit.
Application: International photometry, scientific measurements, and transitional standard between imperial and metric systems.
A CGS unit of illumination. 1 phot = 10,000 lux. Represents one lumen per square centimeter. Rarely used in modern applications.
Historical context: Part of the CGS photometric system, primarily found in older scientific literature and vintage equipment specifications.
The illumination from a one-candle light source at a distance of one centimeter. 1 cm·c = 10,000 lux = 1 phot. CGS unit for very close light measurements.
Application: Microscopy lighting, close-range photometric measurements, and specialized optical work.
The fundamental SI definition of illumination based on luminous flux. 1 lm/m² = 1 lux. Direct measurement of luminous energy density on a surface.
Application: Scientific photometry, precise lighting calculations, and optical system design.
Illumination measured as lumens per square foot. 1 lm/ft² ≈ 10.764 lux. Commonly used in North American lighting design alongside foot-candles.
Application: American architectural lighting, workplace illumination standards, and interior design specifications.
A very small unit of illumination. 1 nox = 0.001 lux. Used for measuring extremely dim light conditions.
Application: Astronomical observations, low-light vision research, and night sky measurements.
A historical unit based on candlelight at a standard distance. Rarely used in modern applications and found primarily in historical literature.
Historical note: Defined the illumination from a standard candle at a specific reference distance.