# how many lumens do car headlights output?

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#### **DONOTDELETE**

##### Guest
i'm reading all these things about surefires 15 lum, 65 lum, 225lum, 500 lumens. but i don't know what those mean? how bright is that actually? compared to car headlights?

thanks

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#### Brock

##### Flashaholic
Ok, I don't know but I can get you in the ballpark. The P60 lamp in a Surefire M2 is slightly brighter than my car's headlights. Now my cars headlights cover an area of about 3 feet by 5 feet with a LOT of spill to all sides and the Surefire is about 1 foot by 1 foot, with not to much side spill. So they are close in CP (amount of light at a given spot), but in lumens (overall light output) a cars headlight is much brighter.

Hope this helps

Brock

#### kb0rrg

##### Enlightened
The 12PM and the M6 are in the ball park of 30 watts (according to Brock's page). The average car headlight is 55 watts (for one light). I would assume that this is an incompete analysis of the two systems, but logic would say that the headlight would be 1.83 times more lumens if all others things are equal.

<FONT COLOR="#000000" SIZE="1" FACE="Verdana, Arial">This message has been edited by kb0rrg on 01-21-2001 at 09:28 PM</font>

#### phyhsuts

##### Enlightened
What headlamp? Not all headlamps are equal! The 9006 for example gives 1000lm. A D2S Xenon metal halide arc has about 3000lm. All that are the outputs of the lamps only. The optics do not have 100% efficiency, so the actual output is rather lower. But the outputs quoted by SureFire are also lamp outputs.

#### hmmwv

##### Newly Enlightened
12 P/Z M is closer to 20 W not 30 - the bulb voltage is close to 6V, the current is close to 3.7A (yea - the 12V stack of batteries drops to 6V when you run 3.7A through it, which is why they get so hot!) - the lamp used in the 12Z is rated at 20W from carley.

#### Unicorn

##### Flashlight Enthusiast
I believe that many (if not most) of the spotlights mounted on police cars are about 800 lumens, and a little over 100,000 candlepower. A measurement of lumens by itself is almost worthless, as bad as just candlepower. A 60 lightbulb produces 800 lumens, but it's not focused, a Surefire 6P makes 65 lumens, but is focused fairly tight so is a brighter light. You can't compare different manufacturs light by just the lumen rating since how it is focused will make a large difference. Even from the same maker things could vary. The Turboheads from Surefire for example. The 9P and the 9PT were both 105 lumens, but the turbohead was more tightly focused, and therefore the hotspot was brighter, but a little smaller.

#### phyhsuts

##### Enlightened
Unicorn is absolutely right! That is why I had suggested elsewhere that the best way to compare lights on paper is to do what sports lighting fixture manufacturers do: publish photometric characteristics of their lights. That way there is no need to talk lumens or candelas. Who is going to lead the industry to do that?

#### Unicorn

##### Flashlight Enthusiast
Even if manufacturers would at a minimum publish both the lumen and the candlepower ratings, with the distance the candlepower was measured. That at least would give an idea of how bright, and how focused the beam is. Unfortunately I don't see anything like this happening soon. The manufacturers would then have to be more honest about what they are making. That 15,000 candlepower wouldn't sound so good if you found out that it was measured at only 3 feet, and the lumen rating was only about 35, or that 140 lumens less appealing when it is less than 7,000cp at 30 feet because the beam is so spread out.

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#### **DONOTDELETE**

##### Guest
Comparison among different light sources is impossible. The lumen and candlepower units are based on isotropic (radiating in all directions) radiation. Candlepower is derived from the steradian, a solid angle with its' beginning at the center of the light source, whose angle subtends on the surface of the light source an area equal to the square of the radius of the light source.

Light them up and compare them by eye. It is the only real way to compare. Walt

#### NightShift

##### Enlightened
When i purchased my portable spotlights, they always featured "X times the power of an automobile headlight. My latest spotlight is a 1.5 Million Candlepower. On the box it states "30 times the power of an automobile spotlight." Do the math...1,500,000cp/30 = 50,000 cp for an average automobile headlight based on what the box says

#### Chris M.

##### Flashlight Enthusiast
I was thinking about this the other day, and had an idea- a good universal and easy to understand way to compare flashlight outputs would be the same specifications as LEDs use- Candela/Millicandela rating, and beam angle. Surely that would be easy enough to measure using the same/similar equipment they use for LEDs, and it would give a much better indication of how bright or useful a particular lamp`s output is for the required task.

Just a thought...

#### Unicorn

##### Flashlight Enthusiast
I'm curious as to how goo the rating that REI uses to measure lights they sell is. It's foot candles. I think that they measure the light output one foot from the light. That is similar to what I read foot candles are, the measurement of light output at one foot from the light source. The problem I see is similar to lumens. Both seem to measure total light output, and not "brightness." I guess the best thing is to find a dealer who has the lights you want in stock, and will let you test them.

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#### **DONOTDELETE**

##### Guest
Unicorn; you said:

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>I guess the best thing is to find a dealer who has the lights you want in stock, and will let you test them.<HR></BLOCKQUOTE>

Bingo! You hit the nail on the head. There is no other way to compare lights. Period.

It seems there is still considerable confusion about lumens, lux, foot candles, candelas, and so forth. For a lucid description of light geometry, go
HERE

Hope this helps, Walt

#### Unicorn

##### Flashlight Enthusiast
If I understand correctly, even lights from the same manufacturer can not be compared using the manufacturer supplied data, unless they were measured the exact same way.
I still think that there could be a universal standard. Maybe the sperhical candela, beam candela, and the angle of the beam? I think that would give you the total output, the output of the bright spot, and an idea of how tight, or wide the beam is. And a stnadard distance or distances for measurement. Say 3, 7, and 20 meters?
Am I correct in my thinking? Of course even if I am, it isn't likely that an manufacturer would ever do this.
Oh well, keep posting pics Brock.

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#### **DONOTDELETE**

##### Guest
Unicorn; you are NOT right in your thinking.

'Spherical candela' is redundant. Here is the definition of a candela:

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>The candela is the base unit in light measurement, and is defined as follows: a 1 candela light source emits 1 lumen per steradian in all directions(isotropically). A steradian is defined as the solid angle which, having its vertex at the center of the sphere, cuts off an area equal to the square of its radius.<HR></BLOCKQUOTE>

Thus a candela assumes isotropic radiation.

'Beam candela' is a very confusing and misleading term. Here is a quote from the same source:

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>The biggest source of confusion regarding intensity measurements involves the difference between Mean Spherical Candela and Beam Candela, both of which use the candela unit (lumens per steradian). Mean spherical measurements are made in an integrating sphere, and represent the total output in lumens divided by 4p sr in a sphere. Thus, a one candela isotropic lamp produces one lumen per steradian. Beam candela, on the other hand, samples a very narrow angle and is only representative of the lumens per steradian at the peak intensity of the beam. This measurement is frequently misleading, since the sampling angle need not be defined.<HR></BLOCKQUOTE>

Please note that even beam candela are expressed in steradians; this makes the distance at which the light is measured irrelevant, as it can be easily calculated for any distance using the inverse square law. There ARE two conventional distances, however, one foot and one meter.

Another thing you have overlooked is that all of these measurements are of photopic flux. This is dependent on the color temperature of the light emitted, and also dependent upon whether the eye is dark adapted or not.

Go back and read, really read, the source I provided above. It took me about four or five times before I could make sense of it.

Walt

#### bhvm

##### Newly Enlightened
Going by the average of 30LM/w for Halogens,
My SUV's 130W :tinfoil: main beam gives 130X30= 3900 LM per side.

Thats good for about atleast 7000 Lumens for a car taking into account the optical and focusing losses.

Some people have to do with **** poor 55W bulbs:candle:

#### R@ndom

##### Enlightened
Wow, epic thread necromancy... But incan car headlights aren't going to be 30 l/w. They are designed for longer life and are not driven very hard.

#### Linger

##### Flashlight Enthusiast
yeah, bhvm ... where were you looking that you stumbled upon a thread from 2003?
(I appologize for this question, but: did you notice date of the thread)

#### bshanahan14rulz

##### Flashlight Enthusiast
Linger, it appears that this thread is actually from 2001.

....

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