Convert between various luminance and illuminance units instantly. From candelas per square meter to nits, foot-lamberts to stilbs - essential for display technology, lighting design, and optical engineering.
Formula: nit = cd/m² (equivalent)
Formula: cd/m² = nit (equivalent)
Formula: fL = cd/m² × 0.291864
Formula: cd/m² = fL ÷ 0.291864
Formula: sb = cd/m² ÷ 10,000
Formula: cd/m² = sb × 10,000
Formula: fc = lux × 0.092903
Formula: lux = fc ÷ 0.092903
Luminance and illuminance are fundamental concepts in lighting science and display technology. Luminance measures the brightness of a surface as perceived by the human eye - how much light is emitted or reflected per unit area in a given direction. Illuminance, in contrast, measures how much light falls onto a surface. This professional converter handles both types of measurements, providing instant, accurate conversions essential for lighting designers, display engineers, and photographers.
Candelas per square meter (cd/m²) is the SI unit of luminance. A nit is simply another name for the same unit - they are exactly equivalent. The term "nit" (from Latin "nitere," meaning "to shine") is particularly popular in the display industry. Modern smartphone screens typically achieve 500-1,000 nits for outdoor visibility, while HDR televisions may reach 1,000-4,000 nits for peak brightness. Movie theater screens are much dimmer at 48-80 nits (the SMPTE standard is 48 cd/m²), which is why theaters must be dark.
Foot-lambert (fL) is a unit of luminance commonly used in the American film and television industry. One foot-lambert equals approximately 3.426 cd/m². The SMPTE standard for cinema screens is 14 fL (equivalent to 48 cd/m²), while home theater industry recommendations suggest 12-22 fL for optimal viewing. Professional video monitors are often calibrated to 100 cd/m² (about 29 fL). The foot-lambert remains important in American broadcast standards and theatrical projection specifications.
The stilb (sb) is the CGS unit of luminance, equal to 10,000 cd/m². Because modern displays and lighting rarely reach such extreme brightness levels, the stilb is uncommon in contemporary applications. It was more useful historically when describing very bright sources like carbon arc lamps or the sun itself (which has a luminance of approximately 160,000 cd/m² or 16 stilbs). Today, you might encounter stilbs in older scientific literature or specialized optical research contexts.
While luminance measures brightness of a surface, illuminance measures light falling onto a surface. Lux is the SI unit (lumens per square meter), while foot-candle is the Imperial equivalent (lumens per square foot). One foot-candle equals approximately 10.76 lux. Office lighting standards typically require 300-500 lux (28-46 fc), while detailed work might need 1,000 lux (93 fc). Outdoor daylight ranges from 10,000 to 100,000 lux depending on cloud cover and sun position.