Luminance Converter
Print pageAll Equivalents Reference Table
| Unit | Equivalent Value |
|---|
Photometric Luminance (also known as Surface Brightness, Luminous Intensity Density, or Display Perceived Brightness, symbolized by Lv) measures the luminous intensity emitted, reflected, or transmitted per unit projected surface area in a specified direction (Lv = d2Φv ÷ (dA · &cos;θ · dΩ), where Φv is luminous flux in lumens, dA · &cos;θ is projected surface area, and dΩ is solid angle in steradians). Across smartphone OLED display specifications, HDR TV calibration, commercial cinema projection standards (SMPTE ST 2095), architectural lighting glare evaluation, automotive headlight design, and astronomical night sky brightness measurement, luminance is categorized across four major optical unit families: International System of Units (SI metric fundamental: Candela per Square Meter / cd/m2, Lumen per Sq. Meter per Steradian / lm/(m2·sr), Kilocandela per Square Meter / kcd/m2), Modern Display Engineering units (Nit / nt, Millinit / mnt), Cinema & Photometric Reflectance standards (Foot-Lambert / fL, Lambert / L, Millilambert / mL, Apostilb / asb, Blondel), and Legacy CGS / Vision Perception metrics (Stilb / sb, Candela per Square Centimeter / cd/cm2, Candela per Square Inch / cd/in2, Skot, Bril).
Our free online Luminance Converter provides instant, high-precision conversions across all SI metric, modern display nits, cinema foot-lamberts, and optical physics luminance units:
- Nit to Candela per Square Meter [Exact 1:1 Display Identity]:
1 Nit (nt) = 1.0 cd/m2 = 1.0 lm/(m2·sr) = 1,000.0 Millinits (mnt). - Foot-Lambert to cd/m2 & Nits [Cinema Projection Standard]: Multiply fL by
3.4262591(1 fL = 3.42626 cd/m2 = 3.42626 nits ⇒ 1 cd/m2 = 0.2918635 fL). - Lambert to cd/m2 & Nits [Photometric Reflectance Standard]: Multiply Lambert by
3,183.09886(1 L = 3,183.10 cd/m2 = 3,183.10 nits = 1,000 mL = 10,000/π cd/m2). - Stilb to cd/m2 & Nits [CGS High-Brightness Standard]: Multiply stilb by
10,000.0(1 sb = 10,000.0 cd/m2 = 10,000.0 nits = 1.0 cd/cm2 = 10.0 kcd/m2). - Candela per Square Inch to cd/m2 [Imperial Display Unit]: Multiply cd/in2 by
1,550.0031(1 cd/in2 = 1,550.00 cd/m2 = 1,550.00 nits = 144.0 cd/ft2). - Apostilb (Blondel) to cd/m2 [Diffuse Surface Metric]: Multiply asb by
0.318309886(1 asb = 1/π cd/m2 = 0.318310 cd/m2 = 0.318310 nits).
Master Photometric Luminance Conversion Table
The table below displays exact mathematical conversion relationships, SI cd/m2 multipliers, and Display Nits & Foot-Lambert equivalents relative to 1 Candela per Square Meter (1 cd/m2 = 1 Nit = 0.291864 fL):
| Photometric Luminance Unit Name | Symbol | Exact Value in cd/m2 | Display Nits & Foot-Lambert Equivalent | Domain & Technical Application Standard |
|---|---|---|---|---|
| 1 Candela per Square Meter | cd/m2 |
1.0 cd/m2 (Base SI Unit) |
1.0 Nit (0.291864 fL / 1.0 lm/(m2·sr) / 3.14159 asb) |
SI Fundamental Photometric Surface Luminance Standard |
| 1 Nit | nit, nt |
1.0 cd/m2 |
1.0 Nit (100% mathematically equal to 1.0 cd/m2) |
Global Display Engineering (TVs, Smartphones, Monitors) |
| 1 Foot-Lambert | fL, ft-L |
3.4262591 cd/m2 |
3.42626 Nits (3.42626 cd/m2 / 0.318310 cd/ft2) |
US Cinema Projection & Flight Simulator Display Standard |
| 1 Lambert | L |
3,183.09886 cd/m2 |
3,183.10 Nits (929.030 fL / 1,000 mL / 10,000 asb) |
CGS Photometric Reflectance Metric (Named for Lambert) |
| 1 Stilb (cd/sq. centimeter) | sb, cd/cm2 |
10,000.0 cd/m2 |
10,000.0 Nits (2,918.64 fL / 10.0 kcd/m2 / π Lambert) | CGS High-Brightness Source & Lamp Filament Metric |
| 1 Candela per Square Inch | cd/in2 |
1,550.0031 cd/m2 |
1,550.00 Nits (452.389 fL / 0.15500 sb / 144 cd/ft2) | US Imperial Lamp & LED Matrix Surface Brightness |
| 1 Apostilb (Blondel) | asb |
0.31830989 cd/m2 |
0.318310 Nits (0.092903 fL / 0.0001 Lambert) | European Metric Diffuse Surface Luminance Unit |
Step-by-Step Display Screen Brightness & Cinema fL Calculation Example
To convert a commercial cinema projector screen calibrated to 14 Foot-Lamberts (14 fL) under SMPTE ST 2095 standards, and an outdoor smartphone OLED screen rated at 2,400 Nits (2,400 cd/m2) into equivalent units:
Step 1 (Cinema Screen to Nits): Luminance Lv = 14 fL × 3.4262591 = 47.9676 cd/m2 (48 Nits)
Step 2 (Smartphone OLED to Foot-Lamberts): Luminance Lv = 2,400 Nits × 0.2918635 = 700.47 Foot-Lamberts (700 fL)
Step 3 (Smartphone OLED to Candela per Sq. Inch): Lv = 2,400 Nits ÷ 1,550.0031 = 1.5484 cd/in2
Thus, the cinema screen operates at 48 Nits, while the smartphone OLED screen delivers 2,400 Nits (over 50 times brighter than a cinema screen!).
Real-World Display & Optical Luminance Benchmarks
Below is a comparative reference chart showing surface luminance values (Lv) across human perception thresholds, cinema screens, displays, and astronomical sources:
| Light Source / Display Medium | Luminance in Nits (cd/m2) | Foot-Lamberts & Imperial (fL / cd/in2) | Display Engineering & Vision Perception Context |
|---|---|---|---|
| Human Eye Perception Threshold (Scotopic Vision) | 10-6 cd/m2 (0.000001 Nits) | 0.00000029 fL (31.8 Brils) | Absolute rod-cell visual threshold in total darkness |
| Full Moon Night Sky Reflectance | 0.001 cd/m2 (0.001 Nits) | 0.00029 fL (3.14 Skots) | Clear night sky illuminated by full moonlight |
| Standard Commercial Cinema Projector Screen | 48.0 cd/m2 (48.0 Nits) | 14.0 Foot-Lamberts (14.0 fL) | SMPTE ST 2095 theatrical projection brightness target |
| Standard SDR Laptop & Desktop Monitor | 250.0 – 350.0 Nits (cd/m2) | 73.0 – 102.2 fL (0.16 – 0.23 cd/in2) | Standard office desktop indoor display brightness |
| Modern Flagship Outdoor OLED Smartphone (Sunlight) | 1,000.0 – 2,600.0 Nits | 291.9 – 758.8 fL (0.645 – 1.677 cd/in2) | Direct outdoor sunlight peak legibility OLED brightness |
| HDR10+ / Dolby Vision Master Reference Monitor | 1,000.0 – 4,000.0 Nits | 291.9 – 1,167.5 fL (0.645 – 2.58 cd/in2) | Professional video mastering high-dynamic-range monitor |
| Surface of Solar Sun Disk (Noon Sky Direct View) | 1.6 × 109 cd/m2 (1.6 Billion Nits) | 4.67 × 108 fL (160,000 Stilbs sb) | Extreme astronomical surface brightness of solar disk |
History & Physics: 1760 Johann Lambert Cosine Law vs 1948 CGPM Display Nits
1760 Johann Heinrich Lambert & Lambert’s Cosine Law (I = I0 · &cos;θ)
In 1760, German polymath Johann Heinrich Lambert published Photometria, formulating Lambert’s Cosine Law: the luminous intensity observed from an ideal diffusely reflecting surface is directly proportional to the cosine of the angle θ between the observer’s line of sight and the surface normal. Lambert established that an ideal diffuse surface appears equally bright from all viewing angles, defining the Lambert (L) and Foot-Lambert (fL) units.
1948 CGPM Standardization & The Origin of the “Nit”
In 1948, the 9th General Conference on Weights and Measures (CGPM) adopted the Candela per Square Meter (cd/m2) as the official SI unit of luminance. French photometrists coined the informal term nit (derived from the Latin verb nitere, meaning “to shine”). Today, “nits” is the dominant industry standard metric used across Apple, Samsung, Sony, LG, and DisplayMate hardware benchmarking.
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Frequently Asked Questions (FAQ)
Is 1 Nit identical to 1 cd/m2?
Yes, 1 Nit (nt) is 100% mathematically identical to 1 Candela per Square Meter (1 cd/m2). Both units measure exactly the same photometric surface luminance (1 nit = 1.0 cd/m2 = 1.0 lm/(m2·sr)).
How do you convert Foot-Lamberts (fL) to Nits (cd/m2)?
To convert Foot-Lamberts to Nits (cd/m2), multiply fL by 3.4262591. For example, a 14 fL cinema screen × 3.42626 = 48.0 Nits.
How many Nits is a good screen brightness for outdoor sunlight use?
For comfortable outdoor smartphone legibility under direct sunlight, a display screen should deliver at least 1,000 Nits of peak brightness. Flagship OLED smartphones reach peak outdoor brightness between 1,750 and 2,600 Nits.
What is the difference between Luminance (cd/m2) and Illuminance (Lux)?
Luminance (cd/m2 or Nits) measures light emitted or reflected FROM a surface toward an observer’s eyes. Illuminance (Lux or lm/m2) measures light falling UPON a surface from a light source.