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Candlepower -- a useful light output measure? Cateye LD1100 v. LD270compared.



 
 
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  #1  
Old March 25th 09, 11:32 PM posted to rec.bicycles.tech
Andre Jute[_2_]
external usenet poster
 
Posts: 10,422
Default 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

Ads
  #2  
Old March 26th 09, 12:17 AM posted to rec.bicycles.tech
Mike Rocket J Squirrel[_2_]
external usenet poster
 
Posts: 62
Default 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
  #3  
Old March 28th 09, 01:37 AM posted to rec.bicycles.tech
Nick L Plate
external usenet poster
 
Posts: 1,114
Default 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
  #4  
Old March 28th 09, 03:08 AM posted to rec.bicycles.tech
Frank Krygowski[_2_]
external usenet poster
 
Posts: 7,511
Default 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
  #5  
Old March 28th 09, 04:11 AM posted to rec.bicycles.tech
Nick L Plate
external usenet poster
 
Posts: 1,114
Default 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.



  #6  
Old March 28th 09, 04:38 PM posted to rec.bicycles.tech
Frank Krygowski[_2_]
external usenet poster
 
Posts: 7,511
Default 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  
Old March 28th 09, 05:24 PM posted to rec.bicycles.tech
Mike Rocket J Squirrel[_2_]
external usenet poster
 
Posts: 62
Default 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  
Old March 28th 09, 05:38 PM posted to rec.bicycles.tech
Andre Jute[_2_]
external usenet poster
 
Posts: 10,422
Default 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
  #9  
Old March 28th 09, 09:11 PM posted to rec.bicycles.tech
Frank Krygowski[_2_]
external usenet poster
 
Posts: 7,511
Default 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  
Old March 28th 09, 11:07 PM posted to rec.bicycles.tech
Mike Rocket J Squirrel[_2_]
external usenet poster
 
Posts: 62
Default 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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