Convert luminance units — candela/m², nit, stilb, foot-lambert and more.
| Unit | Name | Value |
|---|---|---|
| cd/m² | Candela/Square Meter | 3.42626 |
| nt | Nit | 3.42626 |
| sb | Stilb | 0.000342626 |
| L | Lambert | 0.0010763909 |
| cd/ft² | Candela/Square Foot | 0.31831028 |
| cd/in² | Candela/Square Inch | 0.0022104903 |
Formula: Stilb = Foot-Lambert × 0.0003426
Multiply any Foot-Lambert value by 0.0003426 to get Stilb.
Reverse: Foot-Lambert = Stilb × 2919
Common luminance values — factor: 1 fL = 0.0003426 sb
| Foot-Lambert (fL) | Stilb (sb) | Context |
|---|---|---|
| 0.001 fL | 3.426e-07 sb | Dark |
| 0.01 fL | 3.426e-06 sb | Very dim |
| 0.1 fL | 3.426e-05 sb | Dim |
| 1 fL | 0.0003426 sb | 3.43 nit |
| 2 fL | 0.0006853 sb | 6.85 nit |
| 5 fL | 0.001713 sb | 17 nit |
| 14 fL | 0.004797 sb | SMPTE cinema 48 nit |
| 31 fL | 0.01062 sb | HDR cinema 106 nit |
| 50 fL | 0.01713 sb | 171 nit |
| 100 fL | 0.03426 sb | TV studio 343 nit |
| 200 fL | 0.06853 sb | 685 nit |
| 500 fL | 0.1713 sb | 1,713 nit |
| 1000 fL | 0.3426 sb | 3,426 nit |
| 1e+04 fL | 3.426 sb | 34,260 nit |
| 1e+05 fL | 34.26 sb | 342,600 nit |
1 fL = 0.0003426 sb.
nit = cd/m² exactly. Use this as the bridge between SI and legacy units.
Multiply result by 2919 to recover the original fL 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 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.
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.
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 fL = 0.0003426 sb. Reverse: 1 sb = 2919 fL.
All conversions use IEEE 754 double-precision arithmetic, accurate to at least 8 significant figures.