How many lumens from a candle?

[Phaserburn]

of the taper variety; the ultimate incandescent! Just curious how a candle stacks up to various flashlight outputs.

[Doug S]

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Phaserburn said:
of the taper variety; the ultimate incandescent! Just curious how a candle stacks up to various flashlight outputs.

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It will of course vary with wick length, wax type, and probably other factors but it likely will fall in the 5 to 15 lumen range. The bureau of standards folks used to have a description of the construction of the "standard candle" from which intensity measurements were defined before they went to the definition using the black body cavity radiation involving a temperature defined by the melting temperature of platinum. If you search around you may find a description of that "standard candle".

[jtr1962]

A standard candle is defined as giving off one candlepower over 4*pi steradians. Even you do the math, this comes to 12.56636 lumens.

[Doug S]

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jtr1962 said:
A standard candle is defined as giving off one candlepower over 4*pi steradians. Even you do the math, this comes to 12.56636 lumens.

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Actually not true. The physical candle used for the standard for candlepower [a unit of intensity] was not an isotropic source. The candlepower was defined along a horizontal axis relative to the wick. jtr1962 is thinking of the unit Mean Spherical Candle Power [MSCP] another old unit that was in fact 4*pi lumens. The physical candle from which the intensity unit candlepower is derived would have emitted somewhat less than 4*pi lumens.

[jtr1962]

Actually, MSCP was what I meant. I wasn't referring to a physical candle in my post, just to the derivation of the unit candlepower. I know they're not uniform in their illumination.

[Doug S]

BTW, if you want to build one of these candle standards at home, start by harpooning a Sperm Whale. The candle definition includes "constructed so as to burn 7.8 grams per hour of spermaceti..."

[Polar_Hops]

What about the parrifin wax and lox they are experimenting with for rocket fuels? how many candlepower does that put out i wonder. =(

[capnal]

Mark's Standard Handbook for Mechanical Engineers (10th Edition) page 12-99 defines "candela, cd (formerly candle) is the unit of luminous intensity of a light source. One candela is defined as the luminous intensity in a given direction, of a source that emits monochromatic radiation of a frequency 540 x 10(12)HZ (approx. 55 nm) and of which the radiant intensity in that direction 1/683 W per steridan (W/sr)." It goes on to show in table 12.5.1 that a single candle flame is rated at 6.45 cd/in2.