Lambert (unit)

Lambert ( unit symbol : la , but L in the English Wikipedia, can be found in the Slovak Lb ) is the common unit of luminance in the USA , named after the Swiss-Alsatian physicist, mathematician and philosopher Johann Heinrich Lambert :

${\displaystyle {\begin{aligned}1\ \mathrm {la} &={\frac {1}{\pi }}\ \mathrm {sb} \\&={\frac {1}{\pi }}\ \mathrm {\frac {cd}{cm^{2}}} ={\frac {1}{\pi }}\cdot \mathrm {\frac {cd}{ft^{2}}} \cdot \mathrm {\left({\frac {ft}{cm}}\right)^{2}} \approx 929\ \mathrm {fL} \\&={\frac {10^{4}}{\pi }}\ \mathrm {\frac {cd}{m^{2}}} ={\frac {10^{4}}{\pi }}\ \mathrm {nt} =10^{4}\ \mathrm {asb} \end{aligned}}}$

With

• ${\displaystyle \mathrm {sb} }$for the Stilb
• ${\displaystyle \mathrm {cd} }$for the candela
• ${\displaystyle \mathrm {ft} }$for the foot
• ${\displaystyle \mathrm {fL} }$for the footlambert
• ${\displaystyle \mathrm {asb} }$for the apostilb or the blondel
• ${\displaystyle \mathrm {nt} }$for the nit .