stilbs (sb) to lamberts (L) conversion

1 sb = 3.141593 LL → sb
Formula
1 sb = 3.141593 L

Understanding Stilbs to Lamberts Conversion

The stilb (sb) is a CGS luminance unit equal to one candela per square centimeter. The lambert (L) is a related CGS luminance unit equal to (1/π) candela per square centimeter, defined for a perfectly diffuse surface. Because both share the square-centimeter basis, converting stilbs to lamberts is purely the factor of π that separates a direct candela-per-area unit from the diffuse lambert definition.

Conversion Formula

1 sb=3.14159 L1\ \text{sb} = 3.14159\ \text{L}

To convert stilbs to lamberts, multiply by this factor:

L=sb×3.141593\text{L} = \text{sb} \times 3.141593

Step-by-Step Example

Convert 25 stilbs to lamberts.

L=25×3.141593=78.5398 L\text{L} = 25 \times 3.141593 = 78.5398\ \text{L}

How to Convert Stilbs to Lamberts

Apply the single π factor that separates these two CGS luminance units.

  1. Take the stilb value: For example, 25 sb.
  2. Multiply by 3.141593: This is the factor of π between the stilb and the lambert.
  3. Compute: 25×3.141593=78.539825 \times 3.141593 = 78.5398.
  4. State the result: 25 stilbs equals about 78.5398 L.

stilbs to lamberts conversion table

stilbs (sb)lamberts (L)
00
13.141593
26.283185
39.424778
412.56637
515.70796
618.84956
721.99115
825.13274
928.27433
1031.41593
1547.12389
2062.83185
2578.53982
3094.24778
40125.6637
50157.0796
60188.4956
70219.9115
80251.3274
90282.7433
100314.1593
150471.2389
200628.3185
250785.3982
300942.4778
4001256.637
5001570.796
6001884.956
7002199.115
8002513.274
9002827.433
10003141.593
20006283.185
30009424.778
400012566.37
500015707.96
1000031415.93
2500078539.82
50000157079.6
100000314159.3
250000785398.2
5000001570796
10000003141593

What is the stilb?

The stilb is a CGS unit of luminance, describing the brightness of a surface in terms of luminous intensity per unit area. It was widely used in older photometric literature before the SI candela per square metre became standard.

Definition

One stilb is one candela per square centimetre. Since there are ten thousand square centimetres in a square metre, the stilb is a large unit relative to the SI luminance unit.

1 sb=10000 cd/m21\ \text{sb} = 10000\ \text{cd/m}^2

Exactly, 1 sb=1 cd/cm2=104 cd/m2=104 nits1\ \text{sb} = 1\ \text{cd/cm}^2 = 10⁴\ \text{cd/m}^2 = 10⁴\ \text{nits}.

Origin and History

The stilb was introduced by the French physicist André Blondel around 1920, its name taken from the Greek stilbein, "to glitter." It belonged to the centimetre–gram–second system and was used chiefly in continental Europe.

Law and Notable Facts

The stilb is not part of the SI and has largely fallen out of use in favour of the candela per square metre. Because it references the square centimetre, a single stilb represents a very bright surface: the sun's disc at the horizon is on the order of a few hundred stilbs.

Real-World Examples and Conversions

  • A frosted incandescent lamp surface: a few stilbs.
  • The sun's disc viewed from Earth: roughly 160,000 cd/m², or about 16 stilbs.
  • 1 sb=104 cd/m2=104 nits1\ \text{sb} = 10⁴\ \text{cd/m}^2 = 10⁴\ \text{nits}.
  • 1 cd/m2=10−4 sb1\ \text{cd/m}^2 = 10⁻⁴\ \text{sb}.

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 stilb?

One stilb equals π lamberts, about 3.141593 L.

How do I convert lamberts back to stilbs?

Multiply the lambert value by 0.3183099 (which is 1/π). So 3.141593 L equals 1 sb.

Why is the factor exactly π?

Both units use the square centimeter, and the lambert carries a 1/π factor for diffuse emission, so converting from the stilb leaves just a factor of π.

Where are lamberts and stilbs used?

They are historical CGS luminance units; the lambert appeared in older photometry and astronomy texts, though modern work uses candelas per square metre.

What is 4 stilbs in lamberts?

Multiply 4 by 3.141593 to get about 12.5664 L.

People also convert

sb to cd/m2sb to ntsb to asbsb to fL

Complete stilbs conversion table

sb
UnitResult
candelas per square metre (cd/m2)10000 cd/m2
nits (nt)10000 nt
apostilbs (asb)31415.93 asb
lamberts (L)3.141593 L
foot-lamberts (fL)2918.635 fL

Luminance conversions