Convert luminance units — candela/m², nit, stilb, foot-lambert and more.
| Unit | Name | Value |
|---|---|---|
| cd/m² | Candela/Square Meter | 10000 |
| nt | Nit | 10000 |
| L | Lambert | 3.1415915 |
| fL | Foot-lambert | 2918.6343 |
| cd/ft² | Candela/Square Foot | 929.0313 |
| cd/in² | Candela/Square Inch | 6.4516129 |
Formula: Foot-Lambert = Stilb × 2919
Multiply any Stilb value by 2919 to get Foot-Lambert.
Reverse: Stilb = Foot-Lambert × 0.0003426
Common luminance values — factor: 1 sb = 2919 fL
| Stilb (sb) | Foot-Lambert (fL) | Context |
|---|---|---|
| 1.000e-06 sb | 0.002919 fL | Dark sky |
| 1.000e-05 sb | 0.02919 fL | Night scene |
| 0.0001 sb | 0.2919 fL | Very dim |
| 0.001 sb | 2.919 fL | Dim display |
| 0.005 sb | 14.59 fL | Monitor |
| 0.01 sb | 29.19 fL | 100 nit |
| 0.02 sb | 58.37 fL | 200 nit |
| 0.05 sb | 145.9 fL | 500 nit |
| 0.1 sb | 291.9 fL | HDR10 peak |
| 0.2 sb | 583.7 fL | 2000 nit phone |
| 0.5 sb | 1459 fL | 5000 nit |
| 1 sb | 2919 fL | 10,000 nit HUD |
| 10 sb | 2.919e+04 fL | 100,000 nit |
| 100 sb | 2.919e+05 fL | 1 million nit |
| 1.6e+04 sb | 4.67e+07 fL | Sun surface |
1 sb = 2919 fL.
nit = cd/m² exactly. Use this as the bridge between SI and legacy units.
Multiply result by 0.0003426 to recover the original sb value.
Specifies monitor, TV, and smartphone panel brightness in nits (cd/m²) for HDR grading and product specs.
Calibrates projector output to SMPTE standard of 14 foot-Lamberts for optimal image quality.
Calculates luminance of illuminated surfaces in cd/m² to evaluate glare and visual comfort.
Designs head-up displays exceeding 10,000 nits for daylight readability.
Converts between legacy (Lambert, stilb) and SI (cd/m²) units when reviewing historical data.
Specifies outdoor LED sign brightness in nits for visibility across ambient lighting conditions.
The stilb (sb) is the CGS unit of luminance, equal to 1 candela per square centimeter = 10,000 cd/m². The name comes from the Greek stilbein (to glitter). It was defined in the CGS system in 1918 and predates SI luminance units.
Stilbs are found in older scientific and photometric literature, particularly pre-1970s publications on arc lamps, flashtubes, and laser beam characterization. A carbon arc lamp produces about 15,000 sb (150 million cd/m²).
Interesting fact: The term 'stilb' is rarely used in modern practice outside of historical photometry and some laser physics contexts. The sun's surface luminance of ~2 × 10⁵ sb (2 billion cd/m²) was historically expressed in stilbs in astrophysics literature.
The foot-Lambert (fL) is the US customary unit of luminance equal to 1/π candela per square foot ≈ 3.426 cd/m². It replaced the Lambert for cinema and television applications in North America and remains the standard in US projection specifications.
The film industry uses foot-Lamberts universally in North America: SMPTE specifies cinema screens at 14 fL (±3 fL); HDR cinema (Dolby Vision) targets 31 fL; 3D projection requires higher gain screens to compensate for dimming. Television studio monitors have been calibrated to 100 fL historically.
Interesting fact: The 14 fL standard for cinema projection was chosen in the 1950s as a compromise between image brightness and lamp lifetime. Modern laser projectors can maintain 14 fL throughout their lifetime, unlike xenon lamps which dim with age.
Luminance measures how bright a surface appears to a human observer. The SI unit is cd/m² (identical to the nit used in display industry). Older units — Lambert, foot-Lambert, and stilb — remain in cinema, photometry, and legacy specs. Key anchors: 100 cd/m² = SDR reference; 1,000 cd/m² = HDR10 peak; 14 fL = 48 cd/m² = SMPTE cinema standard.
Exact factor: 1 sb = 2919 fL. Reverse: 1 fL = 0.0003426 sb.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.