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

1 cd/m2 = 0.0003141593 LL → cd/m2
Formula
1 cd/m2 = 0.0003141593 L

Understanding candelas per square metre to lamberts Conversion

The candela per square metre (cd/m2), or nit, is the SI unit of luminance describing how bright a surface appears. The lambert (L) is a CGS-based luminance unit defined as 1/π candela per square centimetre, historically used in photometry and vision science. Because a square centimetre is ten thousand times smaller than a square metre and the definition embeds 1/π, one cd/m2 is only a small fraction of a lambert.

Conversion Formula

1 cd/m2=0.0003141593 L1\ \text{cd/m2} = 0.0003141593\ \text{L}

To convert candelas per square metre to lamberts, multiply by this factor:

L=cd/m2×0.0003141593\text{L} = \text{cd/m2} \times 0.0003141593

Step-by-Step Example

Convert 25 candelas per square metre to lamberts.

L=25×0.0003141593=0.00785398 L\text{L} = 25 \times 0.0003141593 = 0.00785398\ \text{L}

How to Convert candelas per square metre to lamberts

Translate an SI nit value into the CGS lambert with these steps.

  1. Note the luminance: Start with the value in cd/m2, for example 25.
  2. Multiply by 0.0003141593: This is the number of lamberts in one cd/m2.
  3. Compute: 25×0.0003141593=0.0078539825 \times 0.0003141593 = 0.00785398.
  4. State the result: 25 cd/m2 equal about 0.00785398 lambert.

candelas per square metre to lamberts conversion table

candelas per square metre (cd/m2)lamberts (L)
00
10.0003141593
20.0006283185
30.0009424778
40.001256637
50.001570796
60.001884956
70.002199115
80.002513274
90.002827433
100.003141593
150.004712389
200.006283185
250.007853982
300.009424778
400.01256637
500.01570796
600.01884956
700.02199115
800.02513274
900.02827433
1000.03141593
1500.04712389
2000.06283185
2500.07853982
3000.09424778
4000.1256637
5000.1570796
6000.1884956
7000.2199115
8000.2513274
9000.2827433
10000.3141593
20000.6283185
30000.9424778
40001.256637
50001.570796
100003.141593
250007.853982
5000015.70796
10000031.41593
25000078.53982
500000157.0796
1000000314.1593

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}.

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.

Frequently Asked Questions

How many lamberts equal one candela per square metre?

One cd/m2 equals about 0.0003141593 lambert (roughly π × 10⁻⁴). The lambert is a large unit, so the value is small.

How do I convert lamberts back to candelas per square metre?

Multiply the lambert value by 3183.099. So 0.0003141593 L return to 1 cd/m2.

Why is a lambert so much larger than a nit?

The lambert is defined per square centimetre and includes a 1/π factor, making one lambert equal to 3183.099 cd/m2, thousands of times a typical nit reading.

Where is the lambert unit encountered?

It appears in older photometry, astronomy, and vision-science texts; modern displays and lighting use candelas per square metre (nits) instead.

What is 25 cd/m2 in lamberts?

It is about 0.00785398 lambert, well under one hundredth of a lambert, reflecting a modest surface brightness.

People also convert

cd/m2 to ntcd/m2 to sbcd/m2 to asbcd/m2 to fL

Complete candelas per square metre conversion table

cd/m2
UnitResult
nits (nt)1 nt
stilbs (sb)0.0001 sb
apostilbs (asb)3.141593 asb
lamberts (L)0.0003141593 L
foot-lamberts (fL)0.2918635 fL

Luminance conversions