NewBie
*Retired*
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Spacemarine said:
I'm sorry NewBie, but I think you got it all wrong...
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NewBie said:
"Candlepower is a way of measuring how much light is produced by a light bulb, LED or by striking an arc in a Carbon-Arc spotlight.
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That's wrong. What you mean is Lumen. Candela is a measure of the light emitted in a particular direction.
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Spacemarine said:
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NewBie said:
LOL.
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I don't know if that means that you agree or disagree with me that your statements were wrong.
The rest of your new post of totally correct, although I doubt that a lot of people undestand the scientific definition of candela
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Actually, I'd snagged that definition off a web page, my bust for not reading it throughly enough. But...
The Term Candles which evolved into Candela:
Originally, each country had its own, and rather poorly reproducible, unit of luminous intensity; it was necessary to wait until 1909 to see a beginning of unification on the international level, when the national laboratories of the United States of America, France, and Great Britain decided to adopt the international candle represented by carbon filament lamps. Germany, at the same time, stayed with the Hefner candle, defined by a flame standard, and equal to about nine-tenths of an international candle.
Thus the unit candle.
There were a number of variations as you can see.
Eventually better standards came about, and a new unit was born, called the candela, where the candles of something was measured in candelas.
At one time it was even called the "New Candle".
The units of luminous intensity based on flame or incandescent filament standards in use in various countries before 1948 were replaced initially by the "new candle" based on the luminance of a Planckian radiator (a blackbody) at the temperature of freezing platinum. This modification had been prepared by the International Commission on Illumination (CIE) and by the CIPM before 1937, and was promulgated by the CIPM in 1946. It was then ratified in 1948 by the 9th CGPM which adopted a new international name for this unit, the candela (symbol cd); in 1967 the 13th CGPM gave an amended version of the 1946 definition.
And they keep changing things still today...
In 1979, because of the experimental difficulties in realizing a Planck radiator at high temperatures and the new possibilities offered by radiometry, i.e., the measurement of optical radiation power, the 16th CGPM (1979) adopted a new definition of the candela:
The candela is the luminous intensity, in a given direction, of a source that emitsmonochromatic radiation of frequency 540 x 10^12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.
I've actually got an old book from the 1920's that described the candlepower in various terms at the time. In one instance, it related to a candle made from specific materials, and dimensions, in a hooded lantern, and a rider had to get on a horse, travel to a certain distance watching the candle, on a new moon, or "moonless night". When he couldn't see it, he'd turn back until he saw it. That amount of light at that distance was called 1 candlepower.
Then there are other definitions that still survive today for Candlepower:
Candlepower
The term candlepower is based on a measurement of the light produced by a pure spermaceti candle weighing one sixth of a pound, burning at a rate of 120 grams per hour. Spermaceti is found in the head of Sperm Whales, and once was used to make candles.
Thats why I said LOL, it's a basket of worms.
Now days most folks use the new dictionary definition of Candlepower, which is, "Luminous intensity expressed in candelas."
Some just refer to it as candelas, and drop the term candlepower, which adds a little confusion to things due to the history...
Spacemarine said:
I'm sorry NewBie, but I think you got it all wrong...
[ QUOTE ]
NewBie said:
"Candlepower is a way of measuring how much light is produced by a light bulb, LED or by striking an arc in a Carbon-Arc spotlight.
[/ QUOTE ]
That's wrong. What you mean is Lumen. Candela is a measure of the light emitted in a particular direction.
[/ QUOTE ]
[ QUOTE ]
Spacemarine said:
[ QUOTE ]
NewBie said:
LOL.
[/ QUOTE ]
I don't know if that means that you agree or disagree with me that your statements were wrong.
The rest of your new post of totally correct, although I doubt that a lot of people undestand the scientific definition of candela
[/ QUOTE ]
Actually, I'd snagged that definition off a web page, my bust for not reading it throughly enough. But...
The Term Candles which evolved into Candela:
Originally, each country had its own, and rather poorly reproducible, unit of luminous intensity; it was necessary to wait until 1909 to see a beginning of unification on the international level, when the national laboratories of the United States of America, France, and Great Britain decided to adopt the international candle represented by carbon filament lamps. Germany, at the same time, stayed with the Hefner candle, defined by a flame standard, and equal to about nine-tenths of an international candle.
Thus the unit candle.
There were a number of variations as you can see.
Eventually better standards came about, and a new unit was born, called the candela, where the candles of something was measured in candelas.
At one time it was even called the "New Candle".
The units of luminous intensity based on flame or incandescent filament standards in use in various countries before 1948 were replaced initially by the "new candle" based on the luminance of a Planckian radiator (a blackbody) at the temperature of freezing platinum. This modification had been prepared by the International Commission on Illumination (CIE) and by the CIPM before 1937, and was promulgated by the CIPM in 1946. It was then ratified in 1948 by the 9th CGPM which adopted a new international name for this unit, the candela (symbol cd); in 1967 the 13th CGPM gave an amended version of the 1946 definition.
And they keep changing things still today...
In 1979, because of the experimental difficulties in realizing a Planck radiator at high temperatures and the new possibilities offered by radiometry, i.e., the measurement of optical radiation power, the 16th CGPM (1979) adopted a new definition of the candela:
The candela is the luminous intensity, in a given direction, of a source that emitsmonochromatic radiation of frequency 540 x 10^12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.
I've actually got an old book from the 1920's that described the candlepower in various terms at the time. In one instance, it related to a candle made from specific materials, and dimensions, in a hooded lantern, and a rider had to get on a horse, travel to a certain distance watching the candle, on a new moon, or "moonless night". When he couldn't see it, he'd turn back until he saw it. That amount of light at that distance was called 1 candlepower.
Then there are other definitions that still survive today for Candlepower:
Candlepower
The term candlepower is based on a measurement of the light produced by a pure spermaceti candle weighing one sixth of a pound, burning at a rate of 120 grams per hour. Spermaceti is found in the head of Sperm Whales, and once was used to make candles.
Thats why I said LOL, it's a basket of worms.
Now days most folks use the new dictionary definition of Candlepower, which is, "Luminous intensity expressed in candelas."
Some just refer to it as candelas, and drop the term candlepower, which adds a little confusion to things due to the history...
