Phot

Phot
Unit system	CGS units
Unit of	Illuminance
Symbol	ph
Conversions
1 ph in ...	... is equal to ...
SI derived unit	10000 lx
SAE units	929 fc

Short description: Measure of illuminance

A phot (ph) is a photometric unit of illuminance, or luminous flux through an area. It is not an SI unit but rather is associated with the older centimetre–gram–second system of units. The name was coined by André Blondel in 1921.^[1]

Metric equivalence:

[math]\displaystyle{ 1\ \mathrm{phot} = 1\ \frac{\mathrm{lumen}}{\mathrm{centimetre}^2} = 10,000\ \frac{\mathrm{lumens}}{\mathrm{metre}^2} = 10,000\ \mathrm{lux} = 10\ \mathrm{kilolux} }[/math]

Metric dimensions:

Illuminance = luminous intensity × solid angle / length²

References

↑ Parry Moon. "System of photometer concepts", in the Journal of the Optical Society of America, volume 32, number 6 (June 1942), doi:10.1364/JOSA.32.000348. – Page 355: "The lumen was proposed by Blondel in 1894 and is now universally accepted. The names, phot and stilb were likewise coined by Blondel (1921) and are in general use on the Continent."

External links

Knowledgedoor, LLC (2005). Library of Units and Constants: Illuminance Quantity. Retrieved 2006-07-21.
Illuminance Converter. Retrieved 2006-07-21.

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[1] Parry Moon. "System of photometer concepts", in the Journal of the Optical Society of America, volume 32, number 6 (June 1942), doi:10.1364/JOSA.32.000348. – Page 355: "The lumen was proposed by Blondel in 1894 and is now universally accepted. The names, phot and stilb were likewise coined by Blondel (1921) and are in general use on the Continent."

[1]

v t e CGS units
Base units	centimetre • gram • second
Derived non EM units	barye • dyne • erg • gal • kelvin • poise • phot • stilb
Derived EMU units	abcoulomb • abhenry • abohm • biot • gauss • gilbert • maxwell • oersted
Derived ESU units	statcoulomb • statvolt

Phot

Topic: Physics

See also

References

External links