Lumens vs. candlepower

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Back in the day all spotlights and flashlights were rated by candlepower. Now everything is rated by lumens or lux. Apparently LED's changed all that. Anyone explain the difference and how do they compare?
 

Lynx_Arc

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Candlepower = light intensity typically measured at one spot, typically the brightest spot there is. Lights that aren't focused are still measured at a small area/spot and thus have lower candlepower ratings.
Lumens = total light output over the entire area lit by the device, focusing light into hot spots doesn't affect lumen output as spill is also measured.
In the past incans being a lot less efficient had rather low lumen output so instead of advertising a light putting out 30 lumens they could put a giant reflector on it and rate it at 10,000 candlepower and lights putting out 60 lumens with huge reflectors you would see candlepower in the millions on them. LED emitters at the start were not very bright and didn't focus their output as tightly so in order to compare the output people tested and rated them 2 ways either by the rated lumen output of the LEDs in them (often inflated) or the actual output of the LED in the device itself.
We no longer have lights that on average have less than 100 lumen output that use candlepower ratings and hotspots to hype them we have LED lights with 1000+ actual lumens with a variety of output patterns.
To put it simply with low lumens in lights you had to have good throw to light up at even a reasonable distance, it was hard to see with 50 lumens at any distance but with 500 lumens you can light up even with a flood at a distance and with some throw way surpass an average incan flashlight with few hundred lumens.
What people do now for throw is use optics and reflectors and gang a bunch of LEDs together to augment a beam and have 10,000 lumens total to throw out there.
 

xxo

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Lumens are an OK measure for lights that do not throw, such as light bulbs and area lights, but mostly irrelevant when it comes to flashlights that project a beam. Candlepower/candela/lux is what tells you how much light your flashlight is sending down range to whatever you are looking at.
 

Lynx_Arc

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Lumens are an OK measure for lights that do not throw, such as light bulbs and area lights, but mostly irrelevant when it comes to flashlights that project a beam. Candlepower/candela/lux is what tells you how much light your flashlight is sending down range to whatever you are looking at.

That is not entirely true as there are a lot of lights out there that do throw that list lumens you then have to compare the light engine that focuses the output into a throwable beam with other lights that use similar setups. I almost forgot about candlepower since the high power spotlights started being replaced by LED models that offer 1000s of lumens the candlepower ratings would probably be in the billions for some now as the incans were listed in the 10+ million range with a lot less lumen output. Some lights list throw distance as part of the ANSI standard but I don't think they require candlepower ratings. The biggest problem with candlepower is a good laser can have high candlepower but not be useful as a lighting device so too small a beam with almost no spill can be useless in some instances but have very high candlepower ratings.
 
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dotCPF

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Lumens (measure of output) = amount of light produced by the light. This determines "power" or traditional brightness.

Candlepower (measure of intensity) = how far the beam can throw depending on how focused/ concentrated the beam is on the light. This determines throw.

Lumens (output) is a property of the LED and how it is driven. Candlepower (intensity) is a property of surface brightness (output of the LED compared to it's physical size) and the setup of the light modifier- be it via a reflector or optic. Output is ultimately finite, with only certain amounts possible per LED/ battery/ driver configuration. Candlepower can be much more variable, as with a given light engine a different sized reflector or optic setup will determine total Candela/ intensity- that is you can always make a reflector bigger to increase candela. A light with higher Candela/ candlepower will not only throw further than a light with less Candela- but can effectively appear brighter at lower outputs as all of it's intensity is more focused into a smaller area.
 
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xxo

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That is not entirely true as there are a lot of lights out there that do throw that list lumens you then have to compare the light engine that focuses the output into a throwable beam with other lights that use similar setups. I almost forgot about candlepower since the high power spotlights started being replaced by LED models that offer 1000s of lumens the candlepower ratings would probably be in the billions for some now as the incans were listed in the 10+ million range with a lot less lumen output. Some lights list throw distance as part of the ANSI standard but I don't think they require candlepower ratings. The biggest problem with candlepower is a good laser can have high candlepower but not be useful as a lighting device so too small a beam with almost no spill can be useless in some instances but have very high candlepower ratings.

I didn't say anything about how they are listed.....I don't know what you are saying about that. Something like if an engine's horse power is listed it means it doesn't have torque?? I don't get it.


Anyway candlepower is the same as candela, they just renamed it to make it sound more scientific as part of the SI system, though the way candlepower and candela are measured and defined have changed over the years.
 
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