# candlepower vs lumens



## trapperjay (May 11, 2009)

How do you, or do you, measure lumens from a known/published candlepower??


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## Oddjob (May 11, 2009)

Welcome to CPF. Next time you accidentally post in the wrong forum just notify a moderator and ask them to move it to the correct one rather than starting a new one. As for you question, I do not know but someone here might.


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## Marduke (May 11, 2009)

You cannot convert candlepower or lux into a measure of lumens.

They measure two completely different things.


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## trapperjay (May 11, 2009)

OK, so a light with published candlepower (80000) and no lumens would need to be scientifically tested for a lumens rating?


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## Marduke (May 11, 2009)

trapperjay said:


> OK, so a light with published candlepower (80000) and no lumens would need to be scientifically tested for a lumens rating?



Yes, or theoretically calculated based off other values not related to candlepower.


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## kramer5150 (May 11, 2009)

trapperjay said:


> How do you, or do you, measure lumens from a known/published candlepower??



There is no conversion... they quantify two completely different elements.

Lux = the light intensity at a given point infront the of the source.
Lumens = the total amount of light emitted from the source.

I don't think there is a conversion between Lux and candlepower


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## Twinkle-Plank (May 12, 2009)

convert lux to lumens http://www.unitconversion.org/illumination/lux-to-lumens-per-square-foot-conversion.html


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## bluepilgrim (May 12, 2009)

You might be able to guestimate: (and see the online convert link warnings). 

http://en.wikipedia.org/wiki/Candela
[...]
Relationship between luminous intensity and luminous flux
If a source emits a known intensity (in candelas) in a well-defined cone, the total luminous flux in lumens can be calculated by taking the number of candelas, and dividing it by the number in the table below that corresponds to the "radiation angle" of the lamp (the full vertex angle of the emission cone). See MR16 for emission angles of some common lamps. Theory Formulas Online converter

Example: A lamp that emits 590 cd with a radiation angle of 40°:
590/2.64 = approximately 223 lumens.
[...]


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## kramer5150 (May 12, 2009)

Twinkle-Plank said:


> convert lux to lumens http://www.unitconversion.org/illumination/lux-to-lumens-per-square-foot-conversion.html



... lumens _per square foot_... I think thats different than total emitted lumens


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## Search (May 13, 2009)

You could convert lux to lumens. It would be extremely complicated but think about it.

If you took a flashlight and shined it on a wall five meters away one spot could have a lux of 5000.

The light could be 100 lumens.

You could find a formula to convert this. 

However, you would have to have a new formula for every flashlight because they all have different beam profiles.

Another light could have a lux of 10000 but only 80 lumens.

Another could have a lux of 5000 but 160 lumens.

One would be a little throwy and the other floody.

It would be complicated.

Better to keep them two separate entities without being able to be converted.

Lumens tells you how much light a flashlight produces and lux tells you how the beam profile is in a general idea.

Depends on how bright the spot is compared to the spill.


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## HKJ (May 14, 2009)

Search said:


> You could convert lux to lumens. It would be extremely complicated but think about it.



Not really, lumen is lux * area

To do it: 
Paint a lot of small squares on a wall
Shine a light on the wall
Measure the lux in each square
Sum the lux*square size for all the squares and you have lumens
Expect rather large tolerances, lux meters are not very exact.

This could be optimized, as long as you have some symmetry in the beam.


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## Juggernaut (May 15, 2009)

I find it easy if your talking about an Incan you can just find the Lumens to watts of that bulb and then multiply by it’s wattage, that’s how I find the output of Incans, if there is a light you want me to tell you how bright it is just give me it’s statistics.


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## ResQTech (May 17, 2009)

In short, no you can't accurately convert one to the other or vice versa... Here's a good read about Candlepower vs. Lumens. Hope that helps!


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