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Candlepower ratings ~ Can one be bamboozled?

Iamme

Philosopher
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In a newspaper flyer that features Christmas gifts, there was this cordless...CORDless mind you... spotlight (flashlight) that was rated at (get ready)... a mind blowing 3 MILlion candlepower. REEEally?! (The caps are intentional).

And get this:The bulb is only 100 watts (halogen)!

*I* own some old fashion (well, from 20 years ago, give or take a few years) Q-Beam flood/spot light that plugged into my cars cirgarette lighter or directly to the battery terminals and I could illuminate a deer hundreds of yards out in a farm field like it was daytime...and IT (get ready) is only rated at something like ( a relative measely) 100,000/200,000 candlepower, depending on if you are on flood or spot light mode.

What I want to know is...if candlepower is the amount of total light dispersed from the light source, or if the rating can apply to a lesser amount of total light that rather instead is concentrated in a smaller area?

Is it possible that my Q-Beam light has more total illumination power than the 3 million cp power light? Or, IS that 3m light packing 15-30 times more total light than what my Q-Beam was. THAT I can't possilby imagine if you were to see how bright... and for hundreds of yards... that light could illuminate. You mean to tell me the 3m cp flashlight could shine equally as bright out to a distance of say 30 x 300 yards?...or 9000 YARDS (not feet...YARDS) away? I can't imagine.

Or is this marketing trickery at work here?
 
From Wikipedia
The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540×1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.
Click to expand...
So, according to this, it depends upon the specific color of the light, the intensity of the light, and the angle of the light. Given this definition, a very strongly directed beam of light in the correct color could have a much higher candela rating than something that works more like a spotlight or a headlamp on a car, without emitting more light.
 
I've never researched this, myself. I have never heard of a candella before. The closest sounding that I have gotten to this is Rexella Van Impe and that half-dressed woman in black who used to host those Dracula movies.

Thanks for the links. I am going to them now.

(Jeff, ya got any snow? We have none (left)! None!)
 
No snow 'cept a few flurries back Sunday week.
And that woman with the black hair and dress with the hooters hangin' out was Elvira.
Candella was her favorite dildo. @ 2 million candlepower.
 
Well...I sped thru the link. So. Candlepower is measured at the source, nowadays...now called candela?, he says? So I'm still confused I guess. Does that new (spotlight) flashlight have more brightness, by ANY standard...by 15 to 30 times! more power, than my Q-Beam?...or not?
 
Ya, that's right. Elvira! Didn't the Oak Ridge Boys sing a song about her? "...my heart is on fire...ELVIRA!" (la la la)

Do either of you two guys own one of those 100/200,000, or later the 500,000, or the later 1 mil , or the now later 3 mil candlepower (candela) lights?
 
I think my post summarized it pretty well. The short answer is no.

A candela (also called candlepower by non-scientific types) is a fairly easily manipulated scale.
 
Zygar said:
I think my post summarized it pretty well. The short answer is no.

A candela (also called candlepower by non-scientific types) is a fairly easily manipulated scale.
Click to expand...

By "no", you mean the new 3 million cp light is not necessarily brighter? )(say out a distance of 2-300 yards, trying to illuminate a deer)

Just hours ago, while at Shopko, and searching for a flashlight for my brotherer in law, the floor dude told me he has already seen a 7.5 mil cp one. He said it was enormous and could light up the entire store in the dark and if you looked at it just for a second, you'd see spots.
 
Two ways to manipulate it:
1. measure it over the smallest possible area, at the absolute brightest point in the beam; that is, manufacture the flashlight so that the beam is as concentrated as possible.
2. Measure it at the peak frequency for that source.

For a real measure of actual light, try the lumen, which is a candela per steradian. There are 4 x pi steradians in the solid angle that comprises every direction from a point. This is why light bulbs' outputs are measured in lumens.
 
Very illuminating.
Praise the Lard, I found the light.
And the link in post #3 was pretty straightforward and designed for students at Texass Tech.
 
Oops, I should have said "an intensity of one candela at every point over a steradian." "Per" is indeed incorrect. The lumen is a derived unit, the candela-steradian (cd x sr).
 
Iamme said:
What I want to know is...if candlepower is the amount of total light dispersed from the light source, or if the rating can apply to a lesser amount of total light that rather instead is concentrated in a smaller area?
Click to expand...
It's not the total amount of light put out in all directions. It's the intensity in a particular direction.

For example, if you use the same 100-watt bulb, but you use a different mirror or lens to focus the light into a tighter beam, then you'd end up with a higher candlepower rating. In the beam, that is. Outside the new narrow beam, where there used to be some light, you'd get no light at all. So the total number of lumens might remain the same.
 
69dodge said:
So the total number of lumens might remain the same.
Click to expand...
Assuming a perfect mirror, it would remain the same; however, in the real world there must be a certain amount of loss of light, offset by heating of the reflector. Just a quibble. The essential point is correct.
 
Like photon torpedos. Rather than having all those lumens just spread all over the radians, they are concentrated in a tight beam of coherent energy, which paradoxically can be viewed as moving much slower than the speed of light, with sparkles all around.
 
So, to put it in mathematical language, candella is flux/radius, lumens is divergence?

Seems like one way to manipulate it would be to place a light sensor right next to the light. Let's say that you have a spotlight that's one meter wide, and you place a light meter one centimeter away. The flux isn't much more than what you would have at 2cm, but you can divide by the "radius" of 1cm, giving a much higher candela.
 
Art Vandelay said:
So, to put it in mathematical language, candella is flux/radius, lumens is divergence?

Seems like one way to manipulate it would be to place a light sensor right next to the light. Let's say that you have a spotlight that's one meter wide, and you place a light meter one centimeter away. The flux isn't much more than what you would have at 2cm, but you can divide by the "radius" of 1cm, giving a much higher candela.
Click to expand...

I understand differently, unless I'm misinterpreting what you wrote.

First, the steradian, a measure of solid angle. It's the fraction of the surface of a sphere. There are 2*pi radians in a circle, and there are 4*pi steradians in a sphere. The regular rectangular area needed to block all rays in a solid angle is proportional to the square of the distance from the origin (it's cone-like.)

Ignoring the whole luminous/radiant (visual effect vs. energy) thing, intensity is Watts per steradian, or the power per section of sphere. Because it's per steradian, the intensity of a point source of light is unaffected by distance*. The power per square meter drops with increased distance, but the number of square meters in a steradian increases at the same rate so it cancels out.

Flux is just a measurement of power. It's the measure of the power of the light traveling through some given fraction of the sphere surrounding the light, for example the whole sphere in the case of the total flux of a light source. An eye has a fixed area, so the solid angle decreases with distance and so does the flux at the eye.

The candela (luminous intensity) just adds a funny function for visual sensitivity and a constant because of the historical one candle's worth of light thing. The lumen is just the (luminous) flux of a one candela point light source over one steradian, or 1/(4*pi) times the total flux of a one candela light.

When measuring the intensity, I assume they are finding the flux across some fixed sensor area. A sensor with area A at distance d subtends a solid angle of A/d^2. If the measured flux is F, the intensity would then be F*d^2/A. So even if the flux didn't change much when decreasing the distance to the light (it should change by exactly the right amount ;)) the intensity would decrease.


* Ignoring atmospheric effects. Does intensity change in a vacuum? This is, do photons do funny things if you leave them along long enough? How quickly does intensity actually drop over distance due to losses from dust/air? I'm guessing not so much for visible light, seeing as how that's what we see with.
 
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