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Candlepower -- a useful light output measure? Cateye LD1100 v. LD270compared.
Yesterday my Cateye TL-LD1100 was incapacitated when some fat bitch
carelessly or maliciously banged my bike with her car door at the supermarket. Fortunately I have a spare rear flasher, Cateye's TL-LD270, which I promptly fitted. The 270 is a tiny light compared to the 1100 which, by modern standards at least, is a biggish light thought not truly a fistful. From a medium distance, 30 or 40 paces, far enough at traffic speeds for a driver to notice and react and slow, the 270 doesn't even in daylight subjectively seem all that much less bright than the 1100 (which is bright enough for use in bright sunshine), though clearly the bigger 1100 attracts attention at greater ranges than the 270 can manage. But here's the kicker. The 270 is said by Cateye to be rated at 4cd or candlepower whereas the 1100 is rated at 100 candlepower. Even keeping in mind that this is a subjective test, and that perceived light does not answer to a linear rule, I must say that cd or candlepower seems to me a rating so unilluminating (intended pun) as to be useless for any practical purpose of consumer comparison. **** For those in the market for a flasher: Buy the bigger LD1100; it is only a few dollars more at the discounters and it is truly a daylight warning lamp. If you're a hyper-weight weenie, or have only a tiny space available, the LD270 appears to be a very good light; it is unfair to any light to compare it to the exceptional LD1100. The discounted price difference of a few dollars isn't even all accounted for by the light output: the 270 has only flashing and steady programmes, whereas the 1100 has a steady and three flashing programmes separately controlled on each row of five powerful LEDs. The 270, incidentally, attaches tidily with Cateye's latest bracket, intended for seatpost attachment, to a 10mm pannier rack strut, which the older bracket on the 1100 won't do; my 1100 was tiewrapped to the racktop bag permanently on the bike. Besides the amount of light produced, and the attachment comparison, the LD1100 has the huge advantage of two LEDS on each side pointing perpendicularly to the side of the bike, and optics that ensure for practical purposes all round visibility. Day or night, a driver would have to be blind not to see the LD1100. ******* While I'm glad to have the TL-LD270 for interim use, and it seems to me a much, much better rear light than comparison of the ratings might indicate, I think I'll order another TL-LD1100 and be certain of being seen. Andre Jute Visit Andre's books at http://www.audio-talk.co.uk/fiultra/THE%20WRITER'S%20HOUSE.html |
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#2
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Candlepower -- a useful light output measure? Cateye LD1100 v.LD270 compared.
I thought that lumens were the correct unit for measuring the brightness
of things like tail lamps? On 3/25/2009 3:32 PM Andre Jute wrote: Yesterday my Cateye TL-LD1100 was incapacitated when some fat bitch carelessly or maliciously banged my bike with her car door at the supermarket. Fortunately I have a spare rear flasher, Cateye's TL-LD270, which I promptly fitted. The 270 is a tiny light compared to the 1100 which, by modern standards at least, is a biggish light thought not truly a fistful. From a medium distance, 30 or 40 paces, far enough at traffic speeds for a driver to notice and react and slow, the 270 doesn't even in daylight subjectively seem all that much less bright than the 1100 (which is bright enough for use in bright sunshine), though clearly the bigger 1100 attracts attention at greater ranges than the 270 can manage. But here's the kicker. The 270 is said by Cateye to be rated at 4cd or candlepower whereas the 1100 is rated at 100 candlepower. Even keeping in mind that this is a subjective test, and that perceived light does not answer to a linear rule, I must say that cd or candlepower seems to me a rating so unilluminating (intended pun) as to be useless for any practical purpose of consumer comparison. **** For those in the market for a flasher: Buy the bigger LD1100; it is only a few dollars more at the discounters and it is truly a daylight warning lamp. If you're a hyper-weight weenie, or have only a tiny space available, the LD270 appears to be a very good light; it is unfair to any light to compare it to the exceptional LD1100. The discounted price difference of a few dollars isn't even all accounted for by the light output: the 270 has only flashing and steady programmes, whereas the 1100 has a steady and three flashing programmes separately controlled on each row of five powerful LEDs. The 270, incidentally, attaches tidily with Cateye's latest bracket, intended for seatpost attachment, to a 10mm pannier rack strut, which the older bracket on the 1100 won't do; my 1100 was tiewrapped to the racktop bag permanently on the bike. Besides the amount of light produced, and the attachment comparison, the LD1100 has the huge advantage of two LEDS on each side pointing perpendicularly to the side of the bike, and optics that ensure for practical purposes all round visibility. Day or night, a driver would have to be blind not to see the LD1100. ******* While I'm glad to have the TL-LD270 for interim use, and it seems to me a much, much better rear light than comparison of the ratings might indicate, I think I'll order another TL-LD1100 and be certain of being seen. Andre Jute Visit Andre's books at http://www.audio-talk.co.uk/fiultra/THE%20WRITER'S%20HOUSE.html -- Mike "Rocket J Squirrel" Bend, Oregon |
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Candlepower -- a useful light output measure? Cateye LD1100 v.LD270 compared.
On 25 Mar, 23:17, Mike Rocket J Squirrel
wrote: I thought that lumens were the correct unit for measuring the brightness of things like tail lamps? Yes. I believe the lumen figure to be taken as the light falling on a point away from the lamp whilst a candela figure is that which is emitted by the lamp emmiter(bulb or LEDs). This would make any candela figure innapropriate. The lumen figure would also require a standard test (set distace, within a set horizontal and vertical deviation, stadard colour, within a lumen range). TJ |
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Candlepower -- a useful light output measure? Cateye LD1100 v.LD270 compared.
On Mar 27, 8:37*pm, Nick L Plate wrote:
Yes. *I believe the lumen figure to be taken as the light falling on a point away from the lamp whilst a candela figure is that which is emitted by the lamp emmiter(bulb or LEDs). *This would make any candela figure innapropriate. *The lumen figure would also require a standard test (set distace, within a set horizontal and vertical deviation, stadard colour, within a lumen range). No, lumens measure the total light output for a light source. http://www.ledtronics.com/TechNotes/...tes.aspx?id=13 has a pretty good explanation for these confusing units of measurement. http://www.westsidesystems.com/rays.html has another one. - Frank Krygowski |
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Candlepower -- a useful light output measure? Cateye LD1100 v.LD270 compared.
On 28 Mar, 02:08, Frank Krygowski wrote:
On Mar 27, 8:37*pm, Nick L Plate wrote: Yes. *I believe the lumen figure to be taken as the light falling on a point away from the lamp whilst a candela figure is that which is emitted by the lamp emmiter(bulb or LEDs). *This would make any candela figure innapropriate. *The lumen figure would also require a standard test (set distace, within a set horizontal and vertical deviation, stadard colour, within a lumen range). No, lumens measure the total light output for a light source. http://www.ledtronics.com/TechNotes/....aspx?id=13has a pretty good explanation for these confusing units of measurement.http://www.westsidesystems.com/rays.htmlhas another one. Dictionary check lumen n a unit of luminuous flux - the light emitted in one second in a solid angle of one steradian from a point that is a radiation source of uniform intensity of one candela. |
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Candlepower -- a useful light output measure? Cateye LD1100 v.LD270 compared.
On Mar 27, 11:11*pm, Nick L Plate wrote:
On 28 Mar, 02:08, Frank Krygowski wrote: On Mar 27, 8:37*pm, Nick L Plate wrote: Yes. *I believe the lumen figure to be taken as the light falling on a point away from the lamp whilst a candela figure is that which is emitted by the lamp emmiter(bulb or LEDs). *This would make any candela figure innapropriate. *The lumen figure would also require a standard test (set distace, within a set horizontal and vertical deviation, stadard colour, within a lumen range). No, lumens measure the total light output for a light source. http://www.ledtronics.com/TechNotes/...aspx?id=13hasa pretty good explanation for these confusing units of measurement.http://www.westsidesystems.com/rays.htmlhasanother one. *Dictionary check lumen n *a unit of luminuous flux - the light emitted in one second in a solid angle of one steradian from a point that is a radiation source of uniform intensity of one candela. Again, the units are confusing. Perhaps the simplest way to understand what lumens measure is to examine a light bulb package. The package of household bulbs I just grabbed said "Total light output: 1600 lumens." That explains it adequately. Reflectors and lenses concentrate those lumens, affecting the number of lumens per steradian. Projecting them onto surfaces affects the number of lumens per square foot or per square meter. But the fundamental amount of light is measured in lumens. - Frank Krygowski |
#7
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Candlepower -- a useful light output measure? Cateye LD1100 v.LD270 compared.
On 3/28/2009 8:38 AM Frank Krygowski wrote:
On Mar 27, 11:11�pm, Nick L Plate wrote: On 28 Mar, 02:08, Frank Krygowski wrote: On Mar 27, 8:37�pm, Nick L Plate wrote: Yes. �I believe the lumen figure to be taken as the light falling on a point away from the lamp whilst a candela figure is that which is emitted by the lamp emmiter(bulb or LEDs). �This would make any candela figure innapropriate. �The lumen figure would also require a standard test (set distace, within a set horizontal and vertical deviation, stadard colour, within a lumen range). No, lumens measure the total light output for a light source. http://www.ledtronics.com/TechNotes/...aspx?id=13hasa pretty good explanation for these confusing units of measurement.http://www.westsidesystems.com/rays.htmlhasanother one. �Dictionary check lumen n �a unit of luminuous flux - the light emitted in one second in a solid angle of one steradian from a point that is a radiation source of uniform intensity of one candela. Again, the units are confusing. Perhaps the simplest way to understand what lumens measure is to examine a light bulb package. The package of household bulbs I just grabbed said "Total light output: 1600 lumens." That explains it adequately. Reflectors and lenses concentrate those lumens, affecting the number of lumens per steradian. Projecting them onto surfaces affects the number of lumens per square foot or per square meter. But the fundamental amount of light is measured in lumens. Thanks, Frank, most helpful. So, what units are the most useful to use to compare apparent brightness of something like a tail light? And what units, if any, are the most likely to be used by the manufacturer in their advertising? One hopes there will be some overlap between the two. -- Mike "Rocket J Squirrel" Bend, Oregon |
#8
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Candlepower -- a useful light output measure? Cateye LD1100 v.LD270 compared.
On Mar 28, 4:24*pm, Mike Rocket J Squirrel
wrote: On 3/28/2009 8:38 AM Frank Krygowski wrote: On Mar 27, 11:11 pm, Nick L Plate wrote: On 28 Mar, 02:08, Frank Krygowski wrote: On Mar 27, 8:37 pm, Nick L Plate wrote: Yes. I believe the lumen figure to be taken as the light falling on a point away from the lamp whilst a candela figure is that which is emitted by the lamp emmiter(bulb or LEDs). This would make any candela figure innapropriate. The lumen figure would also require a standard test (set distace, within a set horizontal and vertical deviation, stadard colour, within a lumen range). No, lumens measure the total light output for a light source. http://www.ledtronics.com/TechNotes/...d=13hasapretty *good explanation for these confusing units of measurement.http://www.westsidesystems.com/rays.htmlhasanotherone. Dictionary check lumen n a unit of luminuous flux - the light emitted in one second in a solid angle of one steradian from a point that is a radiation source of uniform intensity of one candela. Again, the units are confusing. Perhaps the simplest way to understand what lumens measure is to examine a light bulb package. *The package of household bulbs I just grabbed said "Total light output: *1600 lumens." *That explains it adequately. Reflectors and lenses concentrate those lumens, affecting the number of lumens per steradian. *Projecting them onto surfaces affects the number of lumens per square foot or per square meter. *But the fundamental amount of light is measured in lumens. Thanks, Frank, most helpful. So, what units are the most useful to use to compare apparent brightness of something like a tail light? And what units, if any, are the most likely to be used by the manufacturer in their advertising? One hopes there will be some overlap between the two. -- Mike "Rocket J Squirrel" Bend, Oregon Frank has been trying manfully but light measurements are such a minefield, you need to keep your wits about you even after you think you mastered it, and then manufacturers of bike lights still play fast and loose with the numbers in the hope of scoring an undeserved advantage. At least Cateye measures all their lights the same way, so you can compare between Cateye lights. -- Andre Jute |
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Candlepower -- a useful light output measure? Cateye LD1100 v.LD270 compared.
On Mar 28, 12:24*pm, Mike Rocket J Squirrel
wrote: On 3/28/2009 8:38 AM Frank Krygowski wrote: Again, the units are confusing. Perhaps the simplest way to understand what lumens measure is to examine a light bulb package. *The package of household bulbs I just grabbed said "Total light output: *1600 lumens." *That explains it adequately. Reflectors and lenses concentrate those lumens, affecting the number of lumens per steradian. *Projecting them onto surfaces affects the number of lumens per square foot or per square meter. *But the fundamental amount of light is measured in lumens. Thanks, Frank, most helpful. So, what units are the most useful to use to compare apparent brightness of something like a tail light? I think candela (or, for more detail, "beam candela" or "end candela") would probably be the most correct unit. See http://www.lib.uwaterloo.ca/discipli...easurement.pdf at page 37. A candela is a lumen per steradian. And what units, if any, are the most likely to be used by the manufacturer in their advertising? One hopes there will be some overlap between the two. Sadly, I doubt it. I think manufacturers are most likely to use whatever units they think will best sell their product. "Visible for over a mile" seems to be a favorite. - Frank Krygowski |
#10
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Candlepower -- a useful light output measure? Cateye LD1100 v.LD270 compared.
On 3/28/2009 1:11 PM Frank Krygowski wrote:
On Mar 28, 12:24�pm, Mike Rocket J Squirrel wrote: On 3/28/2009 8:38 AM Frank Krygowski wrote: Again, the units are confusing. Perhaps the simplest way to understand what lumens measure is to examine a light bulb package. �The package of household bulbs I just grabbed said "Total light output: �1600 lumens." �That explains it adequately. Reflectors and lenses concentrate those lumens, affecting the number of lumens per steradian. �Projecting them onto surfaces affects the number of lumens per square foot or per square meter. �But the fundamental amount of light is measured in lumens. Thanks, Frank, most helpful. So, what units are the most useful to use to compare apparent brightness of something like a tail light? I think candela (or, for more detail, "beam candela" or "end candela") would probably be the most correct unit. See http://www.lib.uwaterloo.ca/discipli...easurement.pdf at page 37. A candela is a lumen per steradian. And what units, if any, are the most likely to be used by the manufacturer in their advertising? One hopes there will be some overlap between the two. Sadly, I doubt it. I think manufacturers are most likely to use whatever units they think will best sell their product. "Visible for over a mile" seems to be a favorite. - Frank Krygowski I see what you mean. Like, nautical, Irish, Scottish, English, or statue? -- Mike "Rocket J Squirrel" Bend, Oregon |
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