I read that a 60 watt incandesent light bulb is about 800 lumens. But I see LED flashlights on e-bay rated at 5000 lumens. So, I'm guessing the 60 wat t bulb is rated in all directions while the LED flashlight is rated based o n a tiny very bright spot of light. I suppose if you could focus the light on a pin point area, the intensity would be 100,000 lumens. So how does a p erson compare LED flashlights without knowing what area of light they are t alking about?
nah. lumens measure total light output, candelas measure light beam intensity (lasers win that one), and lux measures how intelsely a target is illuminated (NIF probably wins here, but sunlight through non-imaging concentators is a stong contender)
some of those 5000 may be hype. check the datasheets for the LED they claim to use.
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Lumens is the measure of total light output in all directions. Lux or Foot candles is the brightness at some distance. Both compensate for the color sensitivity of the human eye.
If you concentrate the light into a small area, the lux or foot candles will increase drastically, the lumens will remain the same. Actually, since the concentration will be through a lens or bounced off a reflector, there will be some losses resulting in a small decrease in lumens.
Chinese lumens are very much larger than standard lumens. In other words, don't believer the lumens numbers on eBay.
If you want to do your own measuring, buy a Lux meter. I have a few of these which I loan to friends and acquaintances and never see again.
1 lux is equal to 1 lumen/sq-meter. If you produce a spot of light on the wall with an area of 1 square meter, the reading on the lux meter will equal lumens. A 1 sq-meter circle has a diameter of 1.12 meters or 44.1 inches. This will get you in the ballpark for testing advertised lumens claims on most flashlights, bicycle lights, and any light that will generate a spot. It won't work for LED house lights or other area lights that do NOT generate a spot. Just shine the flashlight on the wall until you get a circle of 1.12 meters in diameter and measure the brightness in lux with the lux meter. That's also the lumens output.
Unfortunately, this method is loaded with errors. The light distribution across the spot is not uniform. The edge of the spot is not always clearly defined. LED's lose output when warmed up. Various battery state of charge levels produce different outputs. White LED's come if different color temperatures (colors) which will produce different brightness readings, which is why there are specialized LED lux meters. Lenses and reflectors also lower the output. Do the best you can with adjusting the numbers and you'll probably be fairly close to reality.
You can also get fairly close if you know the current drain of the LED light. A common white LED will produce about 80 lumens/watt of light output (ignoring lens, reflector, and heating losses). Measure the LED current and you'll have a good guess as to the lumens it will produce.
Good lux, er... luck.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
You can also get fairly close if you know the current drain of the LED light. A common white LED will produce about 80 lumens/watt of light output (ignoring lens, reflector, and heating losses). Measure the LED current and you'll have a good guess as to the lumens it will produce.
That's good information. I lost my 1 watt (16 LED) flashlight recently and looking for a replacement. It must have been about 80 Lumens. I have a tabl e lamp with a 8.5 watt LED bulb that is about the same as a 60 watt incande scent. So, it must be about 650 Lumens. I have another small flashlight wit h one AA cell and one bright LED that is pretty good but I want something a little larger and brighter. Around here, there is a swap meet vendor selli ng flashlights so I'll compare them all and get the brightest one. I like t o see the thing before I buy it. Can't do that on e-bay.
I recently was looking as some reflector bulbs for a track-light in my house. The bulbs were available in Halogen or LED. Both said 60 watt equivalant. But the halogen said (something like) 650 lumens and the LED said 540 lumens. How can they rate both as 60 watt equivalant, when the LED one is around 20% less lumens?
Nope. The multiple 5mm white LED flashlights are not very efficient. Luminous efficacy is about 40-50 lumens/watt.
For a replacement, I suggest one of the numerous LiIon 18650 cell, 1 watt LED flashlights found on eBay, Amazon, and elsewhere. The latest Cree LED's run about 120 lumens/watt. I bought a fair number of these flashlights, batteries, and chargers to give a Hanukah presents this year. Flashlights were about $5 to $10. Batteries about $1 to $3. Junk chargers were $1.50 while decent chargers were about $10 and up. There's no way to know of the advertised lumens output is for real, so buy one, test it, and them buy more if it's good. Be prepared for sharp corners, defective mechanical components, intermittent switches, and sloppy assembly.
Maybe. The problem is that lumens is measured at 25C while your table lamp probably runs much hotter. Efficacy drops with increasing temperature. You're table lamp might produce 650 to 850 lumens when first turned on and cold, but after a short while, will tend to dim.
The correct way to measure lumens is with an integrating sphere. These are rather expensive, but can be built using styrofoam or paper mache balls. Here's an example of how it's one measuring a bicycle headlight:
There's also the "integrating PVC pipe" contrivance, which can be useful if properly calibrated.
It's difficult to measure brightness (lux) by eye. Use a Lux Meter: (and a blanket to block stray light from the sun at the swap meet).
Having a super bright flashlight is a bad idea. Besides running down the battery too quickly, it can blind YOU at night with the excessive glare. Some of the better flashlights start off at the lowest intensity. As you punch the duz-it-all button, the light cycles through ever brighter settings. Unfortunately, many flashlights do it the other direction, resulting in instant glare blindness when the flashlight is first turned on.
Read the flashlight reviews on CandlePower Forums: There are also a bunch of video reviews on YouTube.
Again, I suggest something powered by an 18650 LiIon battery. Don't bother with alkaline, NiCd, NiMH, or something that uses C or D batteries.
The eBay flashlights are cheap enough that I can afford to buy one, test it, and buy more if it's any good. I bought a few of these with the bicycle mount for presents: The 3xAAA battery holder went into the trash. I can't find my notes on how many lumens it produced, but I'll reproduce the test in a few minutes.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
A quick test using my indoor test range (kitchen wall) produced about
140 lumens at the center of the 1.12 meter test circle. That's through the flashlight lens at the widest possible setting, which I would guess(tm) has about 15% loss. That yields maybe 165 lumens at the LED. I didn't do any compensation for uneven light distribution across the circle.
Current drain was measured at 0.74A with a loaded voltage of 3.82V. Efficacy is: 165 / 0.74 * 3.82 = 58 lumens/watt Not exactly my predicted 80 lumens/watt but fairly typical of what I've measured in the past. It's certainly nowhere near the advertised
12,000 lumens.
I forgot to mumble something about another nice feature. This flashlight is really made for a 26650 size battery. However, it will work with the more common and cheaper 18650 cells with a plastic sleeve, which I purchased separately:
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Do all 60W incandescent bulbs have the same light output? Is there a federal "60W equivalent" standard? Do marketing departments bend reality to make their product look good? Caveat emptor?
It's to do with the spectral emission. LEDs and Halogen lights have different spectra and colour temperature. Halogen might be 2700K and bright white LED 4000K
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I used to do this sort of stuff in my day job ( camera sensitivity) and even I got confused .
I have a bunch of those except mine say "Ultrafire" on the side. I paid about $3.50/ea in quantities of 10x w/o battery. A few problems:
The crenulated lens mounting is designed to be some kind of weapon (security attack hammer). It has sharp edges which will shred your pocket lining and cut your fingers. I had to take them all apart and file the edges.
The light uses a 14500 cell. Same physical size as a AA cell. The cheap 14500 cells that I bought on eBay do not last very long at full brightness. I have not been able to find a decent 14500 cell.
Several of the switches were defective and not repairable.
Despite all this, I carry one. It's small, the belt clip works very well, and I can put it in my mouth when I need a 3rd hand to old the flashlight.
I just measured the output. 180 lumens at max brightness and widest angle. That's through the lens, which has about 15% loss or 212 lumens without the lens. Current drain is 0.85A at 3.8v. efficacy = 212 / 0.85A / 3.8V = 66 lumens/watt which is on the low side of typical (usually about 80 lumens/watt). Obviously, this is nowhere near the advertised 2000 lumens.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
When LED lighting first appeared, the various vendors had a problem. People bought incandescent lamps by the watt, and LED's by the lumen. There's no fixed conversion factor between watts and lumens. So, a decision had to be made for a common method of selling and comparing lighting. The obvious choice would be to measure everything in lumens but that's not what was chosen, probably for some stupid reason like reducing the cost of relabeling incandescent lights.
Comparing incandescent with LED lighting would have been easy using lumens (after one compensates for differences in color temperature) but not so easy using watts. At the time, incandescent was mostly sold by the power consumed and by whether they were halogen or ordinary lights and maybe the expected lifetime. Only the engineering data sheets had the numbers for spectra and lumens. That works well for incandescent because the efficiency of incandescent lighting hasn't really changed in the last century.
However, LED's are different. The efficacy (lumens/watt) is constantly improving. Early lighting LED's were at best 40 lumens/watt. Today, 100 lumens/watt is common. Vendors were not going to tolerate a specification war, as is now common with EPA gasoline mileage specifications. It was therefore decided to have a fixed table of lumens to "equivalent incandescent watts" based on anticipated efficacy levels when incandescent would be banned and LED would rule supreme. Well, they missed a little on the low side because LED's are tested very differently from incandescent lighting. Despite the known errors, it was decided that a bad guess was acceptable for the average consumer, and a chart was produced: Doing the math, the calculated incandescent efficacy is about: 800 / 60 = 13 lumens/watt which (in my never humble opinion) is slightly on the high side.
Meanwhile LED's are improving in efficacy, making such charts less than useful. Add variations in color temperature, packaging, temperature, industry pressure, etc. I consider 20% error amazingly accurate. Eventually we'll dump the "equivalent incandescent watts" and everything will be measured in lumens. The best you can do for now is check if the vendor supplies numbers for lumens, use lumens for comparisons, forget about watts, and don't compare apples and oranges.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Lumens ratings are so widely abused already that they will be rejected as t he new standard. Something new will have to be invented or reused. And the numbers must be large to satisfy marketing, so perhaps microcandles.
Incandescent have improved some since 1917. Before then we had carbon filam ent, tantalum & osmium then tungsten. We've had coiled then coiled coil, th ough the latter did not become commercial until the 30s. And gas fill. Afte r '17 we got halogen. Then IR coatings on halogen. And the disappearance of the lightbulb repair industry says a fair bit about how much costs have re duced.
One day eveyrone will know how luminous 1000 lumens is, until then I need a way to choose a suitable replacement lamp or the rare occasions that one fails.
Ok, let's see if this light will work as advertised:
- A AAA alkaline cell drawing 350ma will deliver maybe 600 ma-hr (my tests) at an average voltage of 1.2v (assuming zero losses in the switching power supply).
- The flashlight data sheet says it will run 0.5 hrs in high power.
- The flashlight data sheet says it will produce 120 lumens in high power.
- The Cree XP-G2 R5 LED has a very high efficacy[1].
That's better than the advertised 0.5 hr. Looks like it should work.
I had a similar size light that I managed to lose somewhere. It's main advantages were that it was small and very bright. However, it had a single push button control with 7 brightness and flashing levels. Every time I wanted to use it or turn it off, I had to push the tiny button 3 or more times. That got old really fast, so I tended to leave it running too often, which is when the fairly short battery life became a problem. The ThruNite Ti3 above uses a different switching scheme, which looks to me as a generally good idea with one exception. To turn it on/off requires both hands, which might be a problem.
[1] The Cree data sheet at: doesn't specify efficacy (lumens/watt) but it can be calculated. The specs at 0.350A and 2.8V at 85C across the LED = 0.98 watts (Pg
11). R5 produces 139 to 148 lumens (Pg 14). I'll call it 140 lumens. Efficacy = 140 / 0.98 = 143 lumens/watt
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
People have an instinctive feeling for incadescent watts. I know that I want a 100 watt bulb in the garage and a 60 for my reading lamp. It's convenient to have the incandescent watt equivalent on the package.
We still use gallons and feet and horsepower for the same reason, and no revolutionary authority forces us to change.
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John Larkin Highland Technology, Inc
lunatic fringe electronics
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