Comparing lumens and candlepower?

[Unregistered]

Re: Comparing lumens and candlepower?

Thank you all for your help. I now understand.

[the knowhow men]

hid torches

hi there guys i just want to advice you to buy a hid torch because its much brighter than any other halogen search lights.The lights do cost more than a halogen search light but you will able to see the difference.

[Guest]

Re: hid torches

hi there guys i just want to advice you to buy a hid torch because its much brighter than any other halogen search lights.The lights do cost more than a halogen search light but you will able to see the difference.

"The highest-intensity halogen headlamp bulbs, H9 and HIR1, produce 2100 to 2530 lumens from approximately 70 watts at 13.2 volts. A D2S HID burner produces 3200 lumens from approximately 42 watts during stable operation."
so at 33 l/W and 76 l/w you can expect to pay 2.3x more for HID. However, perceived brightness will not be in this 2.3 ratio.

[Unregistered]

Re: Comparing lumens and candlepower?

Divide the lumens by 12.57 to get 1 candlepower. In other words, if the spotlight has less than 12,570,000 lumens, it is not as bright as a 1 million candlepower spotlight.

[JohnS]

Re: Comparing lumens and candlepower?

Divide the lumens by 12.57 to get 1 candlepower. In other words, if the spotlight has less than 12,570,000 lumens, it is not as bright as a 1 million candlepower spotlight.

This relationship is only valid if the light is radiated equally in all directions. By definition, that is not a spot light. The spot pattern solid angle (steradians) must be measured to determine relationship between lumens and candlepower.

[Unregistered]

Re: hid torches

"The highest-intensity halogen headlamp bulbs, H9 and HIR1, produce 2100 to 2530 lumens from approximately 70 watts at 13.2 volts. A D2S HID burner produces 3200 lumens from approximately 42 watts during stable operation."
so at 33 l/W and 76 l/w you can expect to pay 2.3x more for HID. However, perceived brightness will not be in this 2.3 ratio.

Also remember that HID bulbs have a different construction/light throw so Lumens and Candela will be different ratios to Halogen. Have experienced with a set of driving lights and changing the halogen bulbs to HID - dramatically changes the light throw. Sure they are brighter but actually not all that more effective than halogen. The HID makes the spot beam really small in diameter (albeit more concentrated) than halogen and the spread beam is just a mess. Soooo.... if wanting to use HID, buy lamps built to take HID bulbs
Cheerio and hello to all my international friends from me in Australia

[brendan]

Re: Comparing lumens and candlepower?

I think the candlepower is measured at a tiny solid angle / beam angle, like i mean a beam angle of 0.1 or 0.01 degrees. The lights with high candlepower are focussed so that the centre has a very high power per solid angle but that drops down to a much lower value outside the very centre. The candlepower emitted from the whole light is far less than the candlepower emitted at the very centre where the candlepower is maximum.

So the candlepower that is advertised is not the candlepower of the whole light but the maximum candlepower at a tiny point. I think this maximum candlepower specification which occurs only at one tiny point is pretty useless. It cannot be compared directly to lumen at all. You could compare candlepower for the whole light to lumen but that is not advertised.

[KCvale]

Re: Comparing lumens and candlepower?

I know this an old topic and I am not a member here, I happened upon this forum searching for Candle vs Lumen light intensity but figured I'd add what I know for you guys as a 'pay it back' for what I learned here.

I build motorized bicycles and a real safety nut so lights are pretty important, especially a bright flashing daytime running light but good steady night riding light as well and discovered Lithium Ion powered CREE high intensity LED lamps.

First of all an LED only projects light in a ~180º not a 360º angle like any kind of halogen or incandescent bulb and do it with less power so all of the math is wrong and in short you 'can't get there from here' kind of thing.

What I can say is I have a 100,000 CP 12V Halogen spot and a 1200 Lumen CREE 3 LED flashlight with 2 18650 3.7V 3A Lithium Ion batteries in series and it doesn't matter the distance that little $44 'hand torch' beam will overpower that Halogen spot with directional light both being pointed at the same spot and on at the same time.

In short, look at LED lights as they are all measured in Lumen because that is only appropriate measurement and don't even bother with a light measured in CP as it is only as relevant as the candle for lighting itself ;-}

[Unregistered]

Re: Comparing lumens and candlepower?

The 250 lumen MiniMagLite Pro+ supposedly produces only about 20 CP. I also have a big searchlight/flashlite weighing about ten pounds that produces 10,000,000 CP.

BUT... If I set one up 30 feet away from me and look (BRIEFLY!) into the beam, the two seem to be just about equally blinding.

Somehow the 500,000 times difference comparison just doesn't seem to make sense in terms of what people are thinking of when they say "Well, how bright is it?"

[Unregistered]

Re: Comparing lumens and candlepower?

Ok, I have read most of the posts in this thread but I guess I just can't see the light, (pun)
I am looking to install a couple of driving light on my truck. I HAVE two GE Q4631 PAR 36 aircraft landing lights. I have used them on a previous truck. They are rated at 250 watts EACH. I think the issues are obvious. That equates to a total current draw of about 40 amps. That requires a relay box because you don't want to run wire large enough inside the truck and the switch would have to be huge. Also you take up a good percentage of the load capacity of a vehicle.

Enter todays LED aftermarket lights. The problem is that they are rated in lumens. While a lot of posts give formulas to make the comparison, it still doesn't get down to the "brass tacks"

I can get two LED lights rated at 1300 lumens each, the current draw is less than 2 amps each and the lamp life FAR exceeds the aircraft lights. But the bottom line question is whether they will in real life be comparable to the aircraft lights when it comes to lighting up the dark road/

The GE Q4631 lamps are rated at 80K Max Beam Candle Power. Beam spead is 13 degrees at 10 feet horizontal and 12 degrees at 10 feet vertical. The bulb life is only rated at 500 hours.

I can not get similiar specifications on the LED lights. They are the Rigid Duallly series 4 LED lamp.

Anybody out there who can give some real comparitive perspective, please jump in here.

[JohnS]

Re: Comparing lumens and candlepower?

Ok, I have read most of the posts in this thread but I guess I just can't see the light, (pun)
I am looking to install a couple of driving light on my truck. I HAVE two GE Q4631 PAR 36 aircraft landing lights. I have used them on a previous truck. They are rated at 250 watts EACH. I think the issues are obvious. That equates to a total current draw of about 40 amps. That requires a relay box because you don't want to run wire large enough inside the truck and the switch would have to be huge. Also you take up a good percentage of the load capacity of a vehicle.

Enter todays LED aftermarket lights. The problem is that they are rated in lumens. While a lot of posts give formulas to make the comparison, it still doesn't get down to the "brass tacks"

I can get two LED lights rated at 1300 lumens each, the current draw is less than 2 amps each and the lamp life FAR exceeds the aircraft lights. But the bottom line question is whether they will in real life be comparable to the aircraft lights when it comes to lighting up the dark road/

The GE Q4631 lamps are rated at 80K Max Beam Candle Power. Beam spead is 13 degrees at 10 feet horizontal and 12 degrees at 10 feet vertical. The bulb life is only rated at 500 hours.

I can not get similiar specifications on the LED lights. They are the Rigid Duallly series 4 LED lamp.

Anybody out there who can give some real comparitive perspective, please jump in here.

See the formula in post #38. Lots of assumptions, mostly the beam falls off gradually, not sharply at the edges. Taking average of horizontal and vertical beam angle, 12.5 degrees, each landing light is producing about 2940 lumens, focused into spot shape. You would need around 4-5 of the LED lights IF you could get a similar beam shape with them.

If the LED beam is broader, the max intensity would obviously be less

[Rodney]

Re: Comparing lumens and candlepower?

This all sounds quite unnesesarily complicated. If you want to compare lumins and candle power in two similar torches, with similar design of lens, spot, etc, surely the answer is 12.57x.

[JohnS]

Re: Comparing lumens and candlepower?

This all sounds quite unnesesarily complicated. If you want to compare lumins and candle power in two similar torches, with similar design of lens, spot, etc, surely the answer is 12.57x.

Only true for omni-directional light.

If you use that rule of thumb, you will always buy the torch rated in candlepower, no need to bother dividing.

[Unregistered]

Re: Comparing lumens and candlepower?

Ok I have read a lot of the reports of Candlepower to lumens and that candlepower is 1 to 12.57 lumens. So a lumen is not near as a bright as candlepower. But then why is it that when I shine a 150 lumen small flashlight (basically 11 candlepower) down a pitch black hallway that it seems to light up the hallway much brighter and I can see more detail that when I shine a 30,000 candlepower mag-light down the same hallway, both mind you with brand new batteries.

[JohnS]

Re: Comparing lumens and candlepower?

Ok I have read a lot of the reports of Candlepower to lumens and that candlepower is 1 to 12.57 lumens. So a lumen is not near as a bright as candlepower. But then why is it that when I shine a 150 lumen small flashlight (basically 11 candlepower) down a pitch black hallway that it seems to light up the hallway much brighter and I can see more detail that when I shine a 30,000 candlepower mag-light down the same hallway, both mind you with brand new batteries.

Lumens measure total light output. Candlepower measures light in a particular direction. The 12.57 ratio is ONLY correct for a light that is equal bright in ALL directions (NOT a flashlight).

The 150 lumen flashlight is NOT 11 candlepower because it is not omnidirectional, the beam candlepower is MUCH higher. The MagLite is certainly not 377,000 lumens. For a narrow beam, you have to know the beamwidth in degrees, and relate the lumens (total output) to beam candlepower and beam width. Or, you can remove the reflector, and operate "barebulb" so the 12.57 ratio applies.

See post #38 for an approximate relationship between lumens, beam candlepower and beamwidth.
Edit: When beam angle is 360°, the formula gives 12.57 (4*pi) steradians as the solid angle, this is where the 12.57 comes from. For a narrow beam, it is MUCH less.