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Thread: lumens vs. candlepower

  1. #1
    Flashaholic
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    Default lumens vs. candlepower

    I'm delighted and amazed to find this discussion board! I've been a flashlight fanatic for many years and never expected to find a group of people with the same obsession. I have bought many Maglights in the past and am used to light output being expressed in terms of "candlepower". I just bought a Surefire 6P and its light output is signified in terms of "Lumens". What is the relationship between these two terms? How much candlepower, for example, is 65 Lemens? Also, where can replacement lithium batteries be purchased? Thanks.

  2. #2
    Farewell our Curmudgeon Administrator Roy's Avatar
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    Default Re: lumens vs. candlepower

    Are you ready for this?

    From the Webster's Ninth New Collegate Dictonary:

    LUMEN - A unit of luminous flux equal to the light emitted in a unit solid angle by a uniform point source of one candle intensity.

    CANDELPOWER - Luminous intensity expressed in candles.

    CANDLE (aka CANDELA) - A unit of luminous intensity equal to one sixieth of the luminous intensity of one square centimeter of a blackbody surface at the solidification temperature of platinum.

    OK....everybody got that?
    If so, explain it to me! :-)

    As I understand it, candlepower is a measure of BEAM intensity and lumen is the measure of total light OUTPUT.

    OK....you PhD types speak up!

  3. #3
    Flashaholic* Chris M.'s Avatar
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    Default Re: lumens vs. candlepower

    I have always been partial to this explanation from Surefire`s FAQ section.....




    Lumens is what is used to specify the total amount of light coming from any light producing device, and candlepower refers to the highest value of the light intensity to be found anywhere in the lights "beam".

    Lumens tell you how "powerful" the light-producing device is, be it a light bulb of any type, a flashlight, or a car headlight. Candlepower tells you how tightly focused the beam is, assuming the light source has a lens or reflector to focus the light into a beam.

    Lumens can be measured quite accurately, using an instrument called an integrating sphere, and identical lights would all have similar lumen values. It is an important quantity to know when comparing different lighting products, as it tells you how much light each one produces.

    Candlepower can also be measured accurately, using a light intensity meter to measure luminous intensity, and then by applying the appropriate formula, which takes into account how far, the meter is from the light source. The problem is that the value measured depends on where in the beam you take the measurement (the highest value found is what is normally used), and on how well the beam is focused. It is not unusual for candlepower values to vary greatly from unit to unit on otherwise identical lights due to small differences in focusing or reflector tolerances.

    Candlepower specifications (if accurate) are really only useful in comparing lights if the lumen values are also provided. If two lights had similar lumen values and one had a higher candlepower value, what it would mean is that light had a more tightly focused beam. This may or may not be an advantage depending on what the light is to be used for. Using candlepower values alone to compare the "power" of different lights, particularly those from different manufacturers, is likely to be at best misleading, particularly since there is a history of overstating actual candlepower values in the flashlight industry.




    [img]images/icons/grin.gif[/img] [img]images/icons/wink.gif[/img]

  4. #4
    Farewell our Curmudgeon Administrator Roy's Avatar
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    Default Re: lumens vs. candlepower

    STUDENTS!

    I hope you all are taking notes, as there will be a test on this material at the end of the class!

    Chris, that was as good an explanation as I've ever seen.

  5. #5
    Flashaholic* Orion's Avatar
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    Default Re: lumens vs. candlepower

    I understand his question. Strictly from a novice point of view, here's another way to ask the question.

    I have a 'million candlepower' spot light. It can throw a beam quite a ways away (I was camping and testing how far I could see stuff.)

    Question is, if I ALSO had a Surefire 6P or one of the more powerful models, would it light up stuff as well?

    That is the novice way to ask the question. [img]images/icons/smile.gif[/img]

  6. #6
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    Default Re: lumens vs. candlepower

    Well you can check out my site for more "unofficial" rankings of how bright lights are in real life, but a 4 D cell Mag is about 30 lumens. You can spot down a 4 D Cell Mag to a tighter spot them a 6P and it will have more CP, but overall light wise the 6P will be brighter.

    Probably didn't help, oh well...

  7. #7
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    Default Re: lumens vs. candlepower

    Thanks for the info - it was all extremely helpful. I think I understand the difference.
    When I ordered the 6P I also ordered an extra P61 lamp assembly - 120 Lumens. An incredible amount of light for such a small instrument. Part of my flashlite fanaticism may stem from the fact I have a rare kind of night blindness called Albicanas Pumctatus. Any other night blind people out there? Also, can Lithium batteries be bought at hardware stores, etc., or do they have to be ordered?

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    Default Re: lumens vs. candlepower

    They are much cheaper on-line, but if you want to buy them locally I would suggest a chain store like Wal-Mart that has a camera area. They are usually used in cameras, sometimes even called "photo" batteries.

  9. #9
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    Default Re: lumens vs. candlepower

    I've started watching for CR123s after I joined CPF and found that if you're willing to pay upwards of $10 a battery, yes they can be found almost anywhere. I have seen them at the supermarket, Radio Shack, the little True Value hardware store and then places youd expect to find them like K-Mart and Wal-Mart. Never ever have they been any less than $7. I believe True Value wins the True Value award on the batteries at $12.50 a pop!

  10. #10
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    Default Re: lumens vs. candlepower

    Last week I bought a total of 70 @ Panasonic 123's from four of "Ramoncito's" Ebay auctions for $62 plus $14 shipping.

    Even though I have a bunch of 223's for disassembly, the ID of the DB flashlights is narrower than the Surefire / Scorpion / Legend LX lights. The tape I put on these broken 223's makes the DB fit too tight. Thus, I only use untaped naked cells in DB's for the bottom connection that conducts through the body.

  11. #11

    Default Re: lumens vs. candlepower

    <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by lemlux:
    Last week I bought a total of 70 @ Panasonic 123's from four of "Ramoncito's" Ebay auctions for $62 plus $14 shipping.
    <HR></BLOCKQUOTE>

    Lemlux,

    On three occasions I bought 123's on Ebay. In every case the batteries were disappointingly postdated so I no longer buy batteries there.

    I'd be interested to know what sort of luck you've had with battery dates on Ebay?

    Brightnorm

  12. #12
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    Default Re: lumens vs. candlepower

    Candlepower is the light measured at one point. Someone said as an example on here that a laser pointer could have 500,000 CP. Thats all it is. A measurement at one point. do you think a laser pointer will be useful to use as a flashlight? Thats where Lumens comes in. Lumens is the measurement of overall light output. Get what im saying?

  13. #13
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    Default Re: lumens vs. candlepower

    I bought some of these batteries too. They are Panasonic. They aren't dated, but the seller says they are 2009 series.

  14. #14
    Flashaholic* sunspot's Avatar
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    Default Re: lumens vs. candlepower

    <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by lemlux:
    Even though I have a bunch of 223's for disassembly, the ID of the DB flashlights is narrower than the Surefire / Scorpion / Legend LX lights. The tape I put on these broken 223's makes the DB fit too tight. Thus, I only use untaped naked cells in DB's for the bottom connection that conducts through the body.<HR></BLOCKQUOTE>
    I bought a six pack of Energiser 223's from Ebay. They came in a hard plastic shell. I had to cut them open with a scroll saw. This was my first 223 buy. Imagine my surprise when I saw the single cells already wrapped up in plastic. Wahooo!!!

  15. #15
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    Default Re: lumens vs. candlepower

    Sunspot:

    Lucky you. My 223's are all Duracells. Out of maybe 20 packs I've opened so far, all cells were naked except for one cell in one pack that slipped into the production line somehow.

  16. #16
    Flashaholic* jtivat's Avatar
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    Default Re: lumens vs. candlepower

    Hey starlight, take a close look at the Panasonics they should have a date pressed in them it is very hard to see. I bought some from the same source, I think they also said they where 2009 and mine are dated 11-2008 so not bad for the price I paid.

  17. #17
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    Default Re: lumens vs. candlepower

    Jt: You're right, I found the date. I checked 3 or 4 and they were all 11/2008.

  18. #18
    Flashaholic* jtivat's Avatar
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    Default Re: lumens vs. candlepower

    I bet it is the same person, I bought about 150 of them for $1.25 each. They seem fine I have gone through a few in some test with my 12P and they do alright. The SF and Duracell are a little better but the price was right.

  19. #19
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    Default Re: lumens vs. candlepower

    Brightnorm:

    The Duracell 223's I've bought this past 6 months have had a distribution of roughly:

    5 % 2004
    10% 2005
    30% 2007
    20% 2008
    20% 2009
    15% 2010

    The Energizer and Varta 123's I've bought for close to $2.00 @ including shipping had expirations between 2008 and 2010.

    I've only opened up 3 of the 70 individual blister pack Panasonics I bought last week. Each is dated 11/2008. I was scared at first that the "8" was a "0" or a "3", as the first battery was the faintest. The second two were clearly "8", but the left side of this digit on the first is so faint it could conceivably be a "3." Packaging is identical, however.

    The "hard-to-see" date stamp is struck as a light depression running in the black part of the label between the "+" and the "-". I wouldn't have noticed it if it weren't for JT's post.

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