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Thread: Lumens Lies!

  1. #1
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    Lumens Lies!

    Per the following report from Light & Motion it looks like a lot of bike LED headlights outputs are grossly exaggerated. The testing was reportedly done by an independent laboratory but there is no way to tell if the Light & Motion lights were cherry picked for the test. The other brands measured results are mostly pretty lousy compared to claimed Lumens outputs.

    http://www.bikelights.com/images/tes...ta_summary.pdf

    I get the impression that for most LED lights the listed light output is based on LED manufacturers claimed output levels which presume that the driving circuitry is optimized for ideal LED driving voltage and current levels and the LED chip is kept properly cooled to optimum temperature. As LED manufacturers light outputs are apparently based on LED junction temperatures of 25 degrees C there is no way to normally keep an operating high power LED near that temperature. Also most light manufacturers probably do not correct for lens and reflector losses. Unless anti reflective multicoated a front lens will lose about 6 to 10% due to surface reflections. Depending on the batteries used their charge state also will affect results for battery powered lights.

    The only LED headlight makers I know of who clearly claim their Lumens outputs are based on actual testing of production units using an integrating sphere are Niterider and Light & Motion.

    Personally I wish there was a law making false or misleading advertising or published specifications illegal for all products. Of course all the LED lights makers would have to do then is make the disclaimer that light output is based on LED manufacturers ratings. I have seen that done too, mostly by flashlight manufacturers.

    I would also like to see the makers of Dynamo lights provide a light versus speed curve for their lights with a typical dynamo hub. Some of the high power dynamo lights do not reach full output until quite substantial speeds are reached. Examples are the Supernova E3 Triple and the Light On! Dynolight.

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  2. #2
    Senior Member socalrider's Avatar
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    I can see how there seca 900 which has 6 r2 leds can get 900 lumens easily.. R2 can be driven hard and get 200+ lumens per bulb..

    Overstating lumens is just part of the game.. The MS light is rated at 900 but actual output is 600-660 lumens.. I am fine with that. I know that the Manufacturer rates the P7 bulb at 900, so that is what people use to market the light..

    A lot of it is that most drivers for lights are trying to find that balance of brightness vs. runtime.. If you went direct drive, sure they would be bright but the runtime would stink.

  3. #3
    Zoom zoom zoom zoom bonk znomit's Avatar
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    Quote Originally Posted by socalrider View Post
    I know that the Manufacturer rates the P7 bulb at 900, so that is what people use to market the light..
    The P7 is NOT rated as being 900lm. The bin is 800 to 900 which means you wont get more than 900.
    If you're lucky expect 850, assuming it is the bin quoted.

    The problem with lupine lights reportedly is they don't us a MCPCB for LED mounting, just a normal circuit board... hence the LEDs run very hot.

    I have no problem with people quoting bulb lumens as long as the design shows reasonable attention to optics/drivers/and cooling and they quote as bulb lumens not Out The Front (OTF). It makes the calculation easy, you measure your drive current and look up the lumen curve and the bin and chuck them all together. Not too long ago a certain commercial light maker was advertising 900lm from a triple cree XR-E light, he was multiplying the 350mA by 1/.35 to get the 1A lumens... didn't understand the efficiency goes down...

    Take the magicshine which claims 900lm, but the driver runs at 2.4A and the LED is poorly mounted, hence the 400lm estimates its getting. Notice DX sells a lot of top bin LEDs...

    Regarding dynamo lights and speed, not reaching max brightness until you're going at a good clip is a good thing. I don't want 680lm at 10kph.

    Regarding false or misleading advertising, do you not have consumer protection laws where you live?

  4. #4
    Senior Member socalrider's Avatar
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    My Magicshine light seems to brighter than 400 lumens.. It is brighter than the NR Trinewt I have by a fair margin and that is rated at 490 lumens..

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    Senior Member kleinboogie's Avatar
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    The numbers mfgs will publish are based on new LEDs as rated by the LED mfgr. LEDs dim over time and I'm comfortable in saying that no light mfgr runs their lights at 100% duty cycle. I'm more of a DIY person but I can appreciate a good light. I ignore their numbers and just turn the thing on and judge by that. GL

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    Duhhhhhhhhhhhhhhhhh, you don't really think advertisers would lie about their products do you? And Lumens are so subject to companies lying it's insane; it's the same extent of lying that goes on when you buy a stereo at Walmart or Best Buy (or the like) and they claim a 580 total rms watts when in reality it's closer to 75!! It's the same with politicians too!!!!

    Consumer protection laws? Those laws and law makers and agencies are a joke; there is so much false ads on TV and radio it makes my head spin, yet consumer protection law makers know these ads are out there and still don't do anything about them. So good luck in getting any help through any consumer protection agency.

    As far as light output goes your best protection is just to read reviews on various lights, view images of them as the one site you posted, and try to find some on display at an LBS and try them in the store. The best way is to actually try the light on rides IF the LBS will allow you to return if your not satisfied with the output or pattern.

    In my opinion though, most of todays higher output lights put out more light then necessary for road use. You don't need 900 lumens traveling at 25mph, in fact you don't need more then 300, but then again I don't suffer from night blindness and I find that I have plenty of light with just a 13 watt halogen traveling at 25mph. That doesn't mean though that when my light dies that I won't get a brighter one, but would probably get either a 16 to 20 watt halogen or a 200 to 250 lumen led. (EDIT) I do run a helmet light, but it's about 100 lumens in a semi flood pattern, and I run a flasher but only to attract attention, it obviously does not light up the road.

    Do you realize that you can get a light so bright, such as those 700 to 900 and more lums lights, that your eyes pupils are smaller to let in less light due to the brightness of the light reflecting off the pavement back into your eyes that the surrounding areas outside of the light pattern are virtually blacked out thus you can see very little detail going on in the unlighted or dimly unlighted areas? Just a thought.
    Last edited by froze; 11-07-09 at 07:55 AM.

  7. #7
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    Quote Originally Posted by socalrider View Post
    My Magicshine light seems to brighter than 400 lumens.. It is brighter than the NR Trinewt I have by a fair margin and that is rated at 490 lumens..
    Are you sure it is brighter overall? Another major factor in light useability and effective illumination is beam shape and width. A light that is more of a flood than a narrow beam will give a wider view but at reduced brightness in the center of the beam. This can make direct comparisons between lights difficult.

    IMO it would be nice if light manufacturers gave accurate actual lumens output of complete lights as well as photos of beam patterns both on the road and on a vertical surface to help consumers judge beam shape.

    German road vehicle rules for instance require very sharp vertical cutoff on all legal vehicle lights to avoid blinding oncoming drivers. If done properly this puts more light on the road for a given lumens output level.
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  8. #8
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    My real objection to the exaggerated Lumens output of many LED lights is that it makes it hard to compare lights and few people are prepared to disassemble a light and measure actual voltage and current to the LEDs as suggested by znomit. Even if you can measure those there is the matter of junction temperature under operating conditions. Also the efficiency of the optics, including the front lens.

    IMO the only accurate way to determine output is via integrating sphere Lumens measurement of a number of production units tested after being on long enough so that the LED temperature has stabilized at close to expected normal operating temperature and reporting the average, or even better the high and low, from the sample.

    As things currently are the Lumens race reminds me of the Detroit horsepower race of the 1960s. The SAE Gross HP method of measurement greatly exaggerated horsepower readings compared to actual in car results and then Marketing was turned loose on the numbers too before they were provided to prospective customers.

    In many areas of the country high end lights are not in stock at bike shops so it is hard to get them except via special order or internet purchase. Inaccurate light output figures from most makers and lack of other information makes comparison shopping almost impossible to do.

    Beam illumination photos on the road or wherever are little help as there is no standard for exposure times or subject matter photographed. This makes comparisons of different makers products difficult too. Thank heavens for sites such as Peter White Cycles which has standardized beam photos of most dynamo headlight beams to give some idea of the differences between various products. Even it needs updating though as some of the photos are of non current versions of the lights. High power LED technology is a fast moving target at the moment.

    Maybe I am being too critical but I worked as a quality assurance, reliability and specification compliance engineer for a division of Xerox for years. As we were selling primarily to the OEM market we had to provide accurate verified specifications for our products.
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