What is a lumen? Candlepower? A Footcandle? A Lux?

[BigJ]

PS: a steradian is a measure of solid angle. This is where my comments about using lumens to compare lights doesn't really work, because you'd have to know the (solid) angle the lumen rating references.

 

[swoop1156]

Yeah, that's what I thought...lumen and candlepower are the same thing; just different. Like a wife and girlfriend. Same thing only different.

 

[whisler151]

Whisler, a lumen is defined by candlepower. The formula is

lumens = steradian * candelas.

Candela is Latin for candle, and directly equates to candlepower.

I see what you are saying, however you are taking things out of context. What it comes down to is that lumens are a measure of the total output from a light source and candlepower is a measure of lighting concentration in a light beam.

Again, its like my horsepower to torque comparison, they both have to do with making the car move forward but measure two totally different things.

If you use the math, one candlepower is equal to aprox 12.57 lumens. So with that math my four 8" 130w KC lights (two 375k candlepower spots and two 175k candlepower floods) equal over 13.8 million lumens? That means that my four KC lights put out over 690 times more light than a Rigid 40" led bar?

 

[BigJ]

Hmm I'm not following ya whisler. Horsepower is a number derived from torque. Horsepower = torque * rpm/5,252. A dyno measures torque and then calculates horsepower from it. Horsepower is not measured, its calculated.

I'm not seeing how that relates to lumens or footcandles?

 

[swoop1156]

I think his analogy was maybe not a good one seeing as how we're doing math and calculations? That's why I used a wife and girlfriend.

Both female. (Both lights)
Both can have kids. (Same output - create light)
One can take half your shit and the other can't! (Lumens vs. Candlepower)

 

[whisler151]

Hmm I'm not following ya whisler. Horsepower is a number derived from torque. Horsepower = torque * rpm/5,252. A dyno measures torque and then calculates horsepower from it. Horsepower is not measured, its calculated.

I'm not seeing how that relates to lumens or footcandles?

I was trying to convey that candlepower and lumens measure two different things...just like horsepower and torque (maybe not a good analogy).

I really dont care about lighting enough to continue arguing. I'm out.

 

[BigJ]

What it comes down to is that lumens are a measure of the total output from a light source and candlepower is a measure of lighting concentration in a light beam.

Maybe its the terminology, but I I don't think that's true. Think of it this way: technically speaking lumens are measurements taken at what you're lighting up. Candlepower is a measurement taken at the surface of the bulb.

 

[BigJ]

Roger that swoop.

Its all good whisler. This can be tricky stuff.

 

[swoop1156]

Roger that swoop.

Hahahah!

 

[BigJ]

:d:d:d