0.291864
1
cd/m²
0.291864
1
cd/m²
The Luminance Converter converts between units of luminance, which measures the luminous intensity per unit area of light emitted or reflected by a surface. The SI unit is candela per square meter (cd/m²), also called the nit. The common imperial unit is the foot-lambert (fL).
Luminance is what the human eye actually perceives as "brightness" of a surface. Unlike illuminance (which measures light falling on a surface), luminance measures light leaving a surface — either emitted by a display or reflected from a surface. It is the key parameter for display technology, cinema projection, road lighting design, and visual ergonomics.
Modern displays have dramatically increased luminance levels: a typical LCD monitor provides 250–400 cd/m² (nits), HDR TVs reach 1,000–4,000 nits, and outdoor LED signs may exceed 5,000–10,000 nits. Smartphone screens in direct sunlight mode can reach 1,000–2,500 nits.
The relationship between cd/m² and foot-lamberts: 1 fL = 3.4263 cd/m². The cinema industry uses foot-lamberts for screen brightness standards (SMPTE specifies 14 fL ± 3 fL for 2D projection). The stilb (sb) and lambert (L) are CGS units that appear in older photometric literature.
The apostilb (asb) equals 1/π cd/m² and represents the luminance of a perfectly diffusing (Lambertian) surface illuminated at 1 lux. It connects illuminance and luminance through the concept of a perfect reflector.
All values are normalized to cd/m². Key conversions: 1 nit = 1 cd/m² (exact), 1 fL = 1/π cd/ft² = 3.4263 cd/m², 1 stilb = 10,000 cd/m², 1 lambert = 10,000/π cd/m² ≈ 3183.1 cd/m², 1 apostilb = 1/π cd/m² ≈ 0.3183 cd/m².
Display brightness comparison: e-reader: 50–100 nits, indoor LCD: 250–400 nits, HDR TV: 1,000–4,000 nits, smartphone outdoor: 1,000–2,500 nits. Cinema standard: 48 cd/m² (14 fL).
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48 cd/m² = 14 fL (cinema standard)
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1000 nits = 0.314 lamberts
A nit is an informal name for candela per square meter (cd/m²), the SI unit of luminance. It is widely used in the display industry to specify screen brightness.
Divide nits by 3.4263. For example, 500 nits = 145.9 foot-lamberts.
A foot-lambert (fL) is a unit of luminance equal to 1/π candela per square foot, or approximately 3.4263 cd/m². It is commonly used in the US cinema and display industries.
For general office use, 250-350 nits is adequate. For HDR content, 600-1000+ nits. For outdoor visibility, 1000+ nits. Professional HDR monitors may reach 1600-4000 nits.
SMPTE ST 196 specifies 14 fL (48 cd/m²) ± 3 fL for white screen luminance in 2D cinema projection. 3D presentations are typically dimmer at 3.5-7 fL.
Illuminance (lux) measures light arriving at a surface. Luminance (cd/m²) measures light leaving a surface (emitted or reflected). Luminance is what the eye perceives as brightness.
A stilb (sb) is a CGS unit of luminance equal to 10,000 cd/m² (1 cd/cm²). It is very large and rarely used in modern practice.
An apostilb (asb) equals 1/π cd/m². It represents the luminance of a perfect Lambertian surface illuminated at 1 lux, connecting illuminance to luminance through diffuse reflection.
In bright ambient conditions, higher display luminance is needed for visibility. A display at 300 nits is comfortable indoors but may be unreadable in direct sunlight without 1000+ nits.
Sustained viewing of surfaces above 10,000-25,000 cd/m² can cause discomfort. Direct sunlight has a luminance of about 1.6 billion cd/m² — never look directly at the sun.
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