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What is the Language of Lighting? What is a Lambert ? ... PDF Print E-mail
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Wednesday, 09 June 2010 17:55


   Between the Courses and the Free material available today we offer books about Electrical Engineering.

   The first lesson is to understand the terms of Light ... between others.

    I am offering the first pages of a book, I purchase from some dollars in the streets of Caracas, by Howard M. Sharp - Introduction to Lighting.

    However, like we generally do, I will offer some definition including What is a Lambert.

    As explain the book, for the purpose of illuminating engineering, light is visually evaluated radiant energy.

    Luminous Flux (F) is the time rate of flow of Light.

    Lumen (lm) is the unit of luminous flux

We have,

Illumination (E)

  • English System - Footcandle (ft-c) - 1 lm per sq ft
  • Metric System:
    • Phot: 1 lum incident per sq cm
    • Lux: 1 lum incident per sq m

Brightness (B)

  • English System
    • Footlambert (ft-L) - 1 lm emitted per sq ft
    • Candle per sq in
  • Metric System:
    • Lambert (L): 1 lum emitted per sq cm
    • Stilb: 1 candle per sq m

Thus, 1 Lambert is the candela per square metre. It due it name to the Swiss mathematician, physicist and astronomer Johann Heinrich Lambert (August 26, 1728 – September 25, 1777).

He was the first to offer a valid proof about the irrationality of π (pi) using continued fractions.

He built an hygrometer to measure humidity.

He is know for his studies with Maps and Mercator projection.

From Wikipedia we have that he works on:


Lambert invented the first practical hygrometer. In 1760, he published a book on light reflection, the Photometria, in which he formulated the law of light absorption—the Beer–Lambert law). Lambert also wrote a classic work on perspective and also contributed to geometrical optics. The photometric unit lambert is named in recognition of his work in establishing the study of photometry.


In his main philosophical work, New Organon (1764), Lambert studied the rules for distinguishing subjective from objective appearances. This connects with his work in the science of optics.


Lambert also developed a theory of the generation of the universe that was similar to the nebular hypothesis that Thomas Wright and Immanuel Kant had (independently) developed. Wright published his account in An Original Theory or New Hypothesis of the Universe (1750), Kant in Allgemeine Naturgeschichte und Theorie des Himmels, published anonymously in 1755. Shortly afterward, Lambert published his own version of the nebular hypothesis of the origin of the solar system in Cosmologische Briefe über die Einrichtung des Weltbaues (1761). Lambert hypothesized that the stars near the sun were part of a group which travelled together through the Milky Way, and that there were many such groupings (star systems) throughout the galaxy. The former was later confirmed by Sir William Herschel.

His works may be downloaded from http://num-scd-ulp.u-strasbg.fr:8080/view/authors/Lambert,_Jean-Henri.html or archive.org.


Giovanni A. Orlando.

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Last Updated on Wednesday, 09 June 2010 18:53