Luminance Converter

Convert light measurements between candela/m², lux, foot-candles, and nits. Perfect for photography, lighting design, and display calibration.

About Luminance Converter

Understanding Light Measurement

Light measurement involves several distinct but related quantities. The candela (cd), the SI base unit for luminous intensity, measures the power of light in a particular direction. From this foundation, we derive other important units: the lumen (lm) for total light output, the lux (lx) for illuminance, and various units for luminance (brightness). These measurements are crucial in lighting design, photography, display technology, and architectural planning.

Common Light Levels

Condition	Illuminance	Description
Full Sunlight	100,000 lx	Direct sun
Daylight	10,000-20,000 lx	Overcast day
Office Lighting	300-500 lx	Typical workspace
Street Lighting	10-20 lx	Night safety

Unit Categories

Luminous Intensity & Flux

Candela (cd): Light intensity
Lumen (lm): Total light output
1 lm = 1 cd × sr (steradian)
LED efficiency: 100-200 lm/W

Illuminance & Luminance

Lux (lx): Light per area
Foot-candle (fc): US unit
Nit (cd/m²): Screen brightness
1 fc = 10.764 lx

Applications

Professional Uses

Architectural lighting design
Photography and cinematography
Display calibration
Workplace safety standards
Scientific research

Display Technology

HDR displays: 1,000+ nits
OLED phones: 400-800 nits
LCD monitors: 200-350 nits
HDR TVs: up to 2,000 nits

Frequently Asked Questions

What are the common units of luminance?

Common luminance units include candela per square meter (cd/m², also called nit), foot-lambert (fL), lambert (L), stilb (sb), and apostilb (asb). The cd/m² is the SI standard. One foot-lambert equals approximately 3.426 cd/m², and one stilb equals 10,000 cd/m². Different industries and regions prefer different units.

How do you convert between nits and foot-lamberts?

To convert nits (cd/m²) to foot-lamberts, divide by 3.426. To convert foot-lamberts to nits, multiply by 3.426. For example, a 500-nit display is approximately 146 foot-lamberts. The foot-lambert is commonly used in the American cinema and projection industry, while nits are the international standard.

What is a stilb and how does it relate to nits?

A stilb (sb) is a CGS unit of luminance equal to one candela per square centimeter, which equals 10,000 cd/m² (nits). The stilb is rarely used in modern practice because it is inconveniently large for most applications. Most lighting and display specifications now use cd/m² or nits as the standard unit.

Why are there so many different luminance units?

Multiple luminance units exist because different measurement systems (SI, CGS, imperial) developed independently, and different industries adopted their preferred units. The cinema industry uses foot-lamberts, the scientific community prefers cd/m², and older European references may use lamberts or apostilbs. Standardization on cd/m² (nits) is increasingly common.

What are typical luminance values for common light sources?

Typical luminance values range widely: the sun's surface is about 1.6 × 10⁹ cd/m², a clear sky is about 8,000 cd/m², a fluorescent lamp surface is about 5,000-10,000 cd/m², a candle flame is about 5,000-15,000 cd/m², and a typical computer monitor is 250-500 cd/m². The human eye can perceive luminance over a range of about 14 orders of magnitude.

Additional Resources

Luminance - Wikipedia Foot-Lambert - Wikipedia Stilb (Unit) - Wikipedia

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