lamberts (L) to candelas per square metre (cd/m2) conversion

1 L = 3183.099 cd/m2cd/m2 → L
Formula
1 L = 3183.099 cd/m2

Understanding Lamberts to Candelas per Square Metre Conversion

The lambert (L) is a CGS luminance unit representing a Lambertian surface emitting 1 lumen per square centimetre. The candela per square metre (cd/m², also called the nit) is the SI unit of luminance and the modern standard for specifying the brightness of displays, screens, and light sources. Converting lamberts to cd/m² lets legacy photometric data be expressed in today's display-industry units, where a typical laptop screen runs a few hundred cd/m².

Conversion Formula

1 L=3183.10 cd/m21\ \text{L} = 3183.10\ \text{cd/m2}

To convert Lamberts to Candelas per Square Metre, multiply by this factor:

cd/m2=L×3183.099\text{cd/m2} = \text{L} \times 3183.099

Step-by-Step Example

Convert 25 Lamberts to Candelas per Square Metre.

cd/m2=25×3183.099=79577.5 cd/m2\text{cd/m2} = 25 \times 3183.099 = 79577.5\ \text{cd/m2}

How to Convert Lamberts to Candelas per Square Metre

Move from the CGS lambert to the SI luminance unit with one multiplication.

  1. Take the lambert value: record the luminance in L.
  2. Multiply by 3183.099: this factor equals 104/π10⁴/\pi and converts to cd/m².
  3. Work the numbers: for 25 L, compute 25×3183.09925 \times 3183.099.
  4. Give the result: the luminance is 79,577.5 cd/m².

lamberts to candelas per square metre conversion table

lamberts (L)candelas per square metre (cd/m2)
00
13183.099
26366.198
39549.297
412732.4
515915.49
619098.59
722281.69
825464.79
928647.89
1031830.99
1547746.48
2063661.98
2579577.47
3095492.97
40127324
50159154.9
60190985.9
70222816.9
80254647.9
90286478.9
100318309.9
150477464.8
200636619.8
250795774.7
300954929.7
4001273240
5001591549
6001909859
7002228169
8002546479
9002864789
10003183099
20006366198
30009549297
400012732400
500015915490
1000031830990
2500079577470
50000159154900
100000318309900
250000795774700
5000001591549000
10000003183099000

What is the Lambert?

The lambert is a non-SI unit of luminance, describing how much light is emitted or reflected from a surface toward an observer. It is named after the Swiss-German polymath Johann Heinrich Lambert and appears mainly in older optics, photometry, and lighting literature.

Definition

The lambert is defined so that a perfectly diffusing (Lambertian) surface emitting or reflecting a total luminous flux of one lumen per square centimetre has a luminance of one lambert.

1 L=3183.10 cd/m21\ \text{L} = 3183.10\ \text{cd/m}^2

Equivalently, 1 L=1π cd/cm2=104π cd/m21\ \text{L} = \frac{1}{\pi}\ \text{cd/cm}^2 = \frac{10⁴{\pi}\ \text{cd/m}^2. The factor of π\pi enters because luminance in candela per unit area relates to the emitted lumens per unit area through the geometry of a Lambertian (cosine-law) emitter. Sub-multiples such as the millilambert (mL) and microlambert are common in practice.

Origin and History

The unit honors Johann Heinrich Lambert (1728–1777), whose 1760 work Photometria laid the mathematical foundations of photometry, including the cosine emission law of diffuse surfaces. The lambert itself was proposed in the early 20th century as photometry was being systematized, and it saw wide use before the SI candela-per-square-metre (nit) became standard.

Law and Notable Facts

The lambert is not part of the SI and is discouraged in modern metrology, but it survives in legacy instruments and texts. A key convenience of the lambert family is that a perfect diffuse reflector illuminated by one lux has a luminance of exactly 1π×10−4\tfrac{1}{\pi}\times10^{-4} lambert, tidily linking illuminance and luminance for ideal surfaces.

Real-World Examples and Conversions

  • A surface of 1 lambert equals about 3183 cd/m², roughly the brightness of a bright fluorescent lamp diffuser.
  • 1 millilambert = 3.18310 cd/m², close to comfortable indoor lighting levels.
  • The closely related foot-lambert (used for cinema screens) equals about 3.426 cd/m²; standard theater screen luminance of 14 fL corresponds to roughly 48 cd/m².
  • 1 lambert ≈ 929.03 foot-lamberts.

What is the candela per square metre?

The candela per square metre is the SI unit of luminance, measuring the luminous intensity emitted or reflected from a surface per unit area in a given direction. It describes how bright a surface appears to the human eye and is the standard used to specify display and screen brightness.

Definition

Luminance is luminous intensity per unit projected area. One candela per square metre is the luminance of a surface emitting one candela of luminous intensity from each square metre of its projected area.

1 cd/m2=1 cd/m21\ \text{cd/m}^2 = 1\ \text{cd/m}^2

As a derived SI unit it can be written 1 cd/m2=1 lm/(m2⋅sr)1\ \text{cd/m}^2 = 1\ \text{lm}/(\text{m}^2 \cdot \text{sr}), since the candela equals one lumen per steradian.

Origin and History

The candela became one of the seven SI base units in 1948 (as the "new candle"), and luminance in candela per square metre followed as the coherent derived unit. It replaced a patchwork of earlier photometric units such as the stilb, lambert, and foot-lambert.

Law and Notable Facts

The candela per square metre is the internationally sanctioned SI unit of luminance and is colloquially known as the "nit." Its value ties to the modern definition of the candela, fixed by the luminous efficacy of monochromatic 540 THz radiation at 683 lm/W.

Real-World Examples and Conversions

  • A typical computer monitor: 200–350 cd/m².
  • A smartphone in bright sunlight mode: 800–2000 cd/m².
  • Clear daytime sky: several thousand cd/m².
  • 1 cd/m2=1 nit=10−4 stilb1\ \text{cd/m}^2 = 1\ \text{nit} = 10⁻⁴\ \text{stilb}.

Frequently Asked Questions

How many candelas per square metre are in one lambert?

One lambert equals 3183.099 cd/m², a value derived from the 104/π10⁴/\pi relationship between the two definitions.

How do I convert lamberts to cd/m²?

Multiply the lambert value by 3183.099. For example, 2 L equals about 6366.20 cd/m².

Why does the factor include the number pi?

The lambert is defined for a perfectly diffusing (Lambertian) surface, and converting its lumen-per-area basis to candela-per-area introduces a factor of 1/π1/\pi, giving 104/π≈3183.09910⁴/\pi \approx 3183.099.

Is cd/m² the same as a nit?

Yes, the nit is simply another name for one candela per square metre, so 1 L also equals 3183.099 nits.

Where is this conversion useful?

It is handy for translating older luminance measurements into the cd/m² units used to spec monitors, TVs, and phone displays today.

People also convert

L to ntL to sbL to asbL to fL

Complete lamberts conversion table

L
UnitResult
candelas per square metre (cd/m2)3183.099 cd/m2
nits (nt)3183.099 nt
stilbs (sb)0.3183099 sb
apostilbs (asb)10000 asb
foot-lamberts (fL)929.0304 fL

Luminance conversions