Candela vs Candlepower

A torch with 300,000 candela is a nice thrower. Then I see these ads for spotlights
boasting say 20 million candlepower.

What’s the difference between candela and candlepower? Both seem to measure throw.

Are candlepower just some made up Chinee unit or some Biblical unit? But then I see the spotlight at the top of the Vegas Luxor to be 40 billion candlepower.

What’s the diff. in these units??

HERE have a read :slight_smile:

For LEDs we only use:

-Lumens for output
-Lux for intensity

So maybe that candlepower is only for HID?

Plus on the other forum I found an answer…they say the candlepower are 30 times (30x) exaggerated.
e.g. a 30 million candlepower would be 1 million candela or a 10 million candlepower would
be about 333,000 cd So they too are way over stated for marketing purposes.

Nowadays candela and candlepower can be considered as being equivalent.
Historically there was a minimal deviation.
The candela has become the official unit. Yes, it’s a good unit for measuring throw.

candela (luminous intensity) measure the total of light which is emitted by the whole device (including reflector or lens)
in a very specific direction (we’re interested in the spot direction).
There’s no difference among source types like HIDs, LEDs or hot wires, it’s just about the light.

And in a certain distance this luminous intensity then results in a certain illuminance,
measured in lux (the further away, the less lux).

But in a distance of 1 meter (~3ft) the numerical value is the same: 1 candela produces 1 lux in one meter distance.
That’s why you often read something like “light has 300,000 lux” while it’s strictly speaking 300,000 cd.
Everybody knows what is meant, but here DrJones explains why candela could be preferred.

lumen (the luminous flux) in contrast measure the total of light which is emitted in all directions, added up.

Both units, candela and lumen, are very useful, but they mean completely different things
and you need both to get at least an idea of the actual beam.
Dragster throwers often optimize candelas and sacrifice lumens :- ) when the spot is very bright (many lux) but tiny (few lumens).

The unresisted exaggerations of candlepower numbers for big hardware store lights are just, mhh, best practice:
It’s “US-hardware-store-CandlePowers” just like it’s China-lumens for some vendors.

candela = candlepower = lux @ 1m

you can also measure lux at different distances, but if you say candela/candlepower you are basically talking about the measurement at 1m only.

Both are a measure of intensity.