Light Touch
From Candle to Candela
Stephen Wilk tells the tale of how the standard unit for luminous intensity evolved.
Filling night-light moulds in a Victorian candle factory. [iStock / Linda Steward]
The candela, as optics and photonics professionals know, is the standard unit of luminous intensity defined by the International System of Units (SIU). It is one of the seven SI base units from which other units are derived. The candela came on the scene in 1948 to replace earlier luminosity units, in particular the “candle,” which was originally based on the light emitted from a spermaceti candle.
…Log in or become a member to view the full text of this article.
This article may be available for purchase via the search at Optica Publishing Group.
Optica Members get the full text of Optics & Photonics News, plus a variety of other member benefits.