"white" LED's vs. incandescent and halogen lights

"white" LED's vs. incandescent and halogen lights

Post by me » Sun, 06 Dec 2009 07:50:04


It's obvious that the mundane "white" LED bicycle lights do not light
up the asphalt roads very well.  Incandescents, halogens, and sodium
lights do better.  There seem to be a lot of oranges and yellows on
the illuminated asphalt surface.

My question is why does it appear this way?

I presume that the yellow-orange-red spectral emissions from the LED's
are weaker than the blues.  The blues are voltage induced while the y-
o-r's are secondary from phosphors in the casing.  Therefore to help
refine my question,

1.  Do the stronger blues in the LED cause the weaker yellow/orange/
reds to be less perceived?

2.  Are the yellows and oranges on the asphalt caused by sulfur
compounds or by dust and dirt embedded in the tarry surface?

 
 
 

"white" LED's vs. incandescent and halogen lights

Post by dlzc » Sun, 06 Dec 2009 09:06:01

Dear me:


Quote:
> It's obvious that the mundane "white" LED bicycle
> lights do not light up the asphalt roads very well.

Emitted watts in the fraction or single digit watts.

Quote:
>?Incandescents, halogens, and sodium lights
> do better.

Tens to hundreds of watts.

Quote:
>?There seem to be a lot of oranges and yellows on
> the illuminated asphalt surface.

> My question is why does it appear this way?

They are painted that way.  People that are not fully color blind can
tell the difference, the paints wear well, and they do not bleach too
fast.

Quote:
> I presume that the yellow-orange-red spectral
> emissions from the LED's are weaker than the
> blues.

The LEDs probably emit only blue, and have the other colors formed by
scattering.  Much like the "white light" from a fluorescent light.

Quote:
>?The blues are voltage induced while the y-
> o-r's are secondary from phosphors in the casing.
>?Therefore to help refine my question,

> 1. ?Do the stronger blues in the LED cause the
> weaker yellow/orange/reds to be less perceived?

No, I believe it is a sensitivity in the eye.  Blue takes more photons
to fire.  Especially for eyes that are triggering mostly rods (black
and white) rather than cones (color).

Quote:
> 2. ?Are the yellows and oranges on the asphalt
> caused by sulfur compounds or by dust and dirt
> embedded in the tarry surface?

Probably just scattering losses.  Energy is lost, which reduces the
wavelength.  And the rod/cone thing.

My two cents.

David A. Smith

 
 
 

"white" LED's vs. incandescent and halogen lights

Post by Nate Nage » Sun, 06 Dec 2009 09:34:44

Quote:

> Dear me:


>> It's obvious that the mundane "white" LED bicycle
>> lights do not light up the asphalt roads very well.

> Emitted watts in the fraction or single digit watts.

>>  Incandescents, halogens, and sodium lights
>> do better.

> Tens to hundreds of watts.

>>  There seem to be a lot of oranges and yellows on
>> the illuminated asphalt surface.

>> My question is why does it appear this way?

> They are painted that way.  People that are not fully color blind can
> tell the difference, the paints wear well, and they do not bleach too
> fast.

>> I presume that the yellow-orange-red spectral
>> emissions from the LED's are weaker than the
>> blues.

> The LEDs probably emit only blue, and have the other colors formed by
> scattering.  Much like the "white light" from a fluorescent light.

>>  The blues are voltage induced while the y-
>> o-r's are secondary from phosphors in the casing.
>>  Therefore to help refine my question,

>> 1.  Do the stronger blues in the LED cause the
>> weaker yellow/orange/reds to be less perceived?

> No, I believe it is a sensitivity in the eye.  Blue takes more photons
> to fire.  Especially for eyes that are triggering mostly rods (black
> and white) rather than cones (color).

>> 2.  Are the yellows and oranges on the asphalt
>> caused by sulfur compounds or by dust and dirt
>> embedded in the tarry surface?

> Probably just scattering losses.  Energy is lost, which reduces the
> wavelength.  And the rod/cone thing.

> My two cents.

> David A. Smith

But if you compare an LED bicycle light to a comparable halogen bicycle
light, you'll prefer the LED.  to paraphrase, "there's no substitute for
more power."

nate

(and injection is nice, but I'd rather...)

--
replace "roosters" with "cox" to reply.
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"white" LED's vs. incandescent and halogen lights

Post by Mark Thorso » Sun, 06 Dec 2009 10:36:16

Quote:

> The LEDs probably emit only blue, and have the other colors formed by
> scattering.  Much like the "white light" from a fluorescent light.

Scattering?  It's fluorescence.  A UV LED e***s
a set of phosphors that emit white light.  That's
what a white LED is.
 
 
 

"white" LED's vs. incandescent and halogen lights

Post by n.. » Sun, 06 Dec 2009 14:30:05


Quote:
> It's obvious that the mundane "white" LED bicycle lights do not light
> up the asphalt roads very well. ?Incandescents, halogens, and sodium
> lights do better. ?There seem to be a lot of oranges and yellows on
> the illuminated asphalt surface.

> My question is why does it appear this way?

> I presume that the yellow-orange-red spectral emissions from the LED's
> are weaker than the blues. ?The blues are voltage induced while the y-
> o-r's are secondary from phosphors in the casing. ?Therefore to help
> refine my question,

> 1. ?Do the stronger blues in the LED cause the weaker yellow/orange/
> reds to be less perceived?

  "White" LEDs have a strong peak in the blue and a nearly Gaussian
curve centered in the green, extending from the blue-green to the red.
They're kinda weak in the tails. Do a Google Image search for "white
led spectrum" and see for yourself.

  The other lamp types you mention are stronger in the red, which the
eye is more sensitive to, particularly at night.

Quote:
> 2. ?Are the yellows and oranges on the asphalt caused by sulfur
> compounds or by dust and dirt embedded in the tarry surface?

  Asphalt may look black to the casual glance, but reflectance spectra
tell the tale:

http://www.geog.utah.edu/~chen/

  Click on the various locations, check out the various surfaces.
Notice for instance "new paving, dark black asphalt, not mixed with
gravel":

http://www.geog.utah.edu/~chen/aspd2.html

  is pretty flat, but "old, dirty asphalt paving":

http://www.geog.utah.edu/~chen/aspa.html

  rises from the short wavelength (blue) to the long wavelength (red)
end.

  ...dirty asphalt just reflects red better.

  Mark L. Fergerson

 
 
 

"white" LED's vs. incandescent and halogen lights

Post by Bill Penros » Sun, 06 Dec 2009 15:00:00


Quote:
> 2. ?Are the yellows and oranges on the asphalt caused by sulfur
> compounds or by dust and dirt embedded in the tarry surface?

I don't see them. I see shades of blue-gray, which is nearly useless
when walking over dark surfaces. Even moonlight is better than white
LEDs.

DB

 
 
 

"white" LED's vs. incandescent and halogen lights

Post by pm » Sun, 06 Dec 2009 15:18:02


Quote:

> > It's obvious that the mundane "white" LED bicycle lights do not light
> > up the asphalt roads very well. ?Incandescents, halogens, and sodium
> > lights do better. ?There seem to be a lot of oranges and yellows on
> > the illuminated asphalt surface.

> > My question is why does it appear this way?

> > I presume that the yellow-orange-red spectral emissions from the LED's
> > are weaker than the blues. ?The blues are voltage induced while the y-
> > o-r's are secondary from phosphors in the casing. ?Therefore to help
> > refine my question,

> > 1. ?Do the stronger blues in the LED cause the weaker yellow/orange/
> > reds to be less perceived?

> ? "White" LEDs have a strong peak in the blue and a nearly Gaussian
> curve centered in the green, extending from the blue-green to the red.
> They're kinda weak in the tails. Do a Google Image search for "white
> led spectrum" and see for yourself.

> ? The other lamp types you mention are stronger in the red, which the
> eye is more sensitive to, particularly at night.

Red map lights are used to preserve dark adaptation because rods _do
not_ respond to them. Rods are most sensitive somewhere in the blue-
green. Do a google image search on "rod sensitivity," etc. Combine
with your previous google image search and you will find that the peak
sensitivity for rods coincides with the "dip" in the typical white LED
spectrum.

-pm

 
 
 

"white" LED's vs. incandescent and halogen lights

Post by Chal » Sun, 06 Dec 2009 17:54:56

Quote:

> It's obvious that the mundane "white" LED bicycle lights do not light
> up the asphalt roads very well. ?Incandescents, halogens, and sodium
> lights do better. ?

"Mundane" 5mm white LEDs are very low-powered-- typically .07 watts
each-- with poor color rendition.  Often, these are overdriven at
around 0.2W to squeeze a bit more light out of them, but this has the
side effect of pushing their color balance farther into the blue
range.

Quality high-flux LEDs like Luxeon, Cree, or Seoul Semiconductor
emitters of nominally 1W or more are not only very bright, but also
very reasonable in their color balance. DiNotte, Niterider, Light &
Motion, Cygolite, Busch & Mueller, and other reputable manufacturers
use high performance, color graded LEDs in their better lights.  The
results are categorically better than incandescents (halogen, krypton,
etc.) of similar power.

Generic 5mm white LEDs cost a few cents each at the wholesale level.
They are excellent in terms of cost-effectiveness and power
efficiency.  But if you want to see things rather than just be seen by
other road users, you'll need either lots of them, or else better
quality lighting.

Chalo

 
 
 

"white" LED's vs. incandescent and halogen lights

Post by n.. » Sun, 06 Dec 2009 18:57:49


Quote:


> > > It's obvious that the mundane "white" LED bicycle lights do not light
> > > up the asphalt roads very well. ?Incandescents, halogens, and sodium
> > > lights do better. ?There seem to be a lot of oranges and yellows on
> > > the illuminated asphalt surface.

> > > My question is why does it appear this way?

> > > I presume that the yellow-orange-red spectral emissions from the LED's
> > > are weaker than the blues. ?The blues are voltage induced while the y-
> > > o-r's are secondary from phosphors in the casing. ?Therefore to help
> > > refine my question,

> > > 1. ?Do the stronger blues in the LED cause the weaker yellow/orange/
> > > reds to be less perceived?

> > ? "White" LEDs have a strong peak in the blue and a nearly Gaussian
> > curve centered in the green, extending from the blue-green to the red.
> > They're kinda weak in the tails. Do a Google Image search for "white
> > led spectrum" and see for yourself.

> > ? The other lamp types you mention are stronger in the red, which the
> > eye is more sensitive to, particularly at night.

> Red map lights are used to preserve dark adaptation because rods _do
> not_ respond to them. Rods are most sensitive somewhere in the blue-
> green. Do a google image search on "rod sensitivity," etc. Combine
> with your previous google image search and you will find that the peak
> sensitivity for rods coincides with the "dip" in the typical white LED
> spectrum.

  The ~430 nm rod peak (beware line wrap):

http://www.ecse.rpi.edu/~schubert/Light-Emitting-Diodes-dot-org/chap1...

  is a bit offset from the LED dip at 475 nm.

http://www.mvlc.info/images/photos/led/spectral3.jpg

  Also, I should have been clearer; cones are more sensitive to red
than to blue.

IMO though WRT the OP's question the deal-breaker is the greater
reflectivity of asphalt in the red independent of light intensity;
illuminated by incandescent etc. lamps it has red-orangish highlights
as the OP says, but under LED illumination it's just black.

  There's also the time factor:

http://www.phys.ufl.edu/~avery/course/3400/vision/dark_adaptation.gif

  If one doesn't ride long enough to get dark-adapted, the greater
sensitivity of the rods doesn't come into play.

  Anyway, isn't the point of a headlight partly to get the rider's
vision out of the scotopic and at least into the mesopic regime?

  Personally I have no problem with bluish LEDs while night biking. To
me it doesn't look "wrong", just different.

  Mark L. Fergerson

 
 
 

"white" LED's vs. incandescent and halogen lights

Post by Brendan Gillat » Sun, 06 Dec 2009 22:45:08

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Quote:

> Dear me:


>> It's obvious that the mundane "white" LED bicycle
>> lights do not light up the asphalt roads very well.

> Emitted watts in the fraction or single digit watts.

>>  Incandescents, halogens, and sodium lights
>> do better.

> Tens to hundreds of watts.

That is an unfair comparison--the _light_ power output of a halogen bulb
is much less than a modern LED for the same electrical power input.

- --
Brendan Gillatt | GPG Key: 0xBF6A0D94
brendan {a} brendangillatt (dot) co (dot) uk
http://www.brendangillatt.co.uk
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"white" LED's vs. incandescent and halogen lights

Post by Mr. Ben » Mon, 07 Dec 2009 00:02:07



Quote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1


>> Dear me:


>>> It's obvious that the mundane "white" LED bicycle
>>> lights do not light up the asphalt roads very well.

>> Emitted watts in the fraction or single digit watts.

>>>  Incandescents, halogens, and sodium lights
>>> do better.

>> Tens to hundreds of watts.

> That is an unfair comparison--the _light_ power output of a halogen bulb
> is much less than a modern LED for the same electrical power input.

The latest LEDs from Cree now produce more than twice the amount of light
that a compact fluorescent tube (CFT - otherwise know as an energy-saving
lamp) produces for the same amount of electrical power.  CFTs produce
around 3-4 times the light of a halogen lamp.
 
 
 

"white" LED's vs. incandescent and halogen lights

Post by Androcle » Mon, 07 Dec 2009 00:19:29


Quote:

> in

>> -----BEGIN PGP SIGNED MESSAGE-----
>> Hash: SHA1


>>> Dear me:


>>>> It's obvious that the mundane "white" LED bicycle
>>>> lights do not light up the asphalt roads very well.

>>> Emitted watts in the fraction or single digit watts.

>>>>  Incandescents, halogens, and sodium lights
>>>> do better.

>>> Tens to hundreds of watts.

>> That is an unfair comparison--the _light_ power output of a halogen bulb
>> is much less than a modern LED for the same electrical power input.

> The latest LEDs from Cree now produce more than twice the amount of light
> that a compact fluorescent tube (CFT - otherwise know as an energy-saving
> lamp) produces for the same amount of electrical power.  CFTs produce
> around 3-4 times the light of a halogen lamp.

The latest fireflies from Nature now produce more than a million times the
amount
 of light that a compact LED produces for even less electrical power.
 
 
 

"white" LED's vs. incandescent and halogen lights

Post by dlzc » Mon, 07 Dec 2009 01:32:37

Dear Brendan Gillatt:

On Dec 5, 6:45?am, Brendan Gillatt

Quote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1


> > Dear me:


> >> It's obvious that the mundane "white" LED bicycle
> >> lights do not light up the asphalt roads very well.

> > Emitted watts in the fraction or single digit watts.

> >> ?Incandescents, halogens, and sodium lights
> >> do better.

> > Tens to hundreds of watts.

> That is an unfair comparison--the _light_ power
> output of a halogen bulb is much less than a modern
> LED for the same electrical power input.

How is that an *unfair* comparison?  The LED energy goes nearly
straight to making light, so you can get light from smaller
batteries.  The other technologies get a subset of mass to a "natural"
emission temperature, so there is significant heat storage (lost at
end-of-cycle), and heat losses while operating.

You can get more light from a halogen (etc) source, because you don't
have to construct it out of unitary cells of "fixed" output.  You just
need a bigger battery...

Not unfair, just physics.

David A. Smith

 
 
 

"white" LED's vs. incandescent and halogen lights

Post by Brendan Gillat » Mon, 07 Dec 2009 02:04:43

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Quote:

> How is that an *unfair* comparison?  The LED energy goes nearly
> straight to making light, so you can get light from smaller
> batteries.  The other technologies get a subset of mass to a "natural"
> emission temperature, so there is significant heat storage (lost at
> end-of-cycle), and heat losses while operating.

Because you are saying that LED lights emit power in the "fraction or
single digit watts" and that "Incandescents, halogens, and sodium lights"
emit with "Tens to hundreds of watts". This is only true if you supply
the former with a smaller amount of electrical energy than the later.
Hence it is an unfair comparison.

Quote:
> You can get more light from a halogen (etc) source, because you don't
> have to construct it out of unitary cells of "fixed" output.  You just
> need a bigger battery...

Huh?

You can make an LED driver of close to 90% efficiency with inputs above
and/or below the battery voltage. There is no need for unitary cells of
fixed output.

- --
Brendan Gillatt | GPG Key: 0xBF6A0D94
brendan {a} brendangillatt (dot) co (dot) uk
http://www.brendangillatt.co.uk
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"white" LED's vs. incandescent and halogen lights

Post by Nate Nage » Mon, 07 Dec 2009 03:30:22

Quote:




>> in

>>> -----BEGIN PGP SIGNED MESSAGE-----
>>> Hash: SHA1


>>>> Dear me:


>>>>> It's obvious that the mundane "white" LED bicycle
>>>>> lights do not light up the asphalt roads very well.
>>>> Emitted watts in the fraction or single digit watts.

>>>>>  Incandescents, halogens, and sodium lights
>>>>> do better.
>>>> Tens to hundreds of watts.
>>> That is an unfair comparison--the _light_ power output of a halogen bulb
>>> is much less than a modern LED for the same electrical power input.

>> The latest LEDs from Cree now produce more than twice the amount of light
>> that a compact fluorescent tube (CFT - otherwise know as an energy-saving
>> lamp) produces for the same amount of electrical power.  CFTs produce
>> around 3-4 times the light of a halogen lamp.

> The latest fireflies from Nature now produce more than a million times the
> amount
>  of light that a compact LED produces for even less electrical power.

Do they come in a dynohub model? :/

nate

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replace "roosters" with "cox" to reply.
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