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

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

Post by pm » Mon, 07 Dec 2009 03:34:36



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.

Maybe you were thinking cones, but still I don't buy it as an
explanation for perceived LED problems. The yellow phosphor is almost
exactly (and not by accident) where you'd want it to be to maximize
luminous efficiency (the CIE y-bar color matching function and the
yellow phosphor both peaking at about 550 nm)

Quote:

> 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.

I think this is part of the problem for sure.
 
 
 

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

Post by dlzc » Mon, 07 Dec 2009 08:29:38

Dear Brendan Gillatt:

On Dec 5, 10:04?am, Brendan Gillatt

Quote:

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


> > 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".

I'm talking about power *draw*.

Quote:
> This is only true if you supply the former with
> a smaller amount of electrical energy than the
> later.

Which is what I was talking about, even though that was absolutely not
clear.

Quote:
> Hence it is an unfair comparison.

As I wrote it, you are correct.

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?

LEDs are, in the cheap ones I have seen, makes of small individual
units.  Maybe they don't have to be, but they have been so far.

Quote:
> 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.

Yes, thank you.  I like LEDs too, in case that was not clear.

David A. Smith

 
 
 

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

Post by Joy Beeso » Mon, 07 Dec 2009 12:25:32

On Fri, 4 Dec 2009 14:50:04 -0800 (PST), me

Quote:

> My question is why does it appear this way?

Because fluorescent LEDs emit light almost exclusively in the
frequencies that hurt, which makes them look glaring-bright when they
are really quite dim.  

--
Joy Beeson
joy beeson at comcast dot net

 
 
 

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

Post by thirty-si » Mon, 07 Dec 2009 13:11:49


Quote:
> On Fri, 4 Dec 2009 14:50:04 -0800 (PST), me


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

> Because fluorescent LEDs emit light almost exclusively in the
> frequencies that hurt, which makes them look glaring-bright when they
> are really quite dim. ?

Which is why my 'old' technology work lamp with 24 LEDs works so well
on urban roads.  The roads are already lit with yellow sodium and the
blueness picks up the colours the yellow does not.   It's stark enough
to stand out from the surroundings as a positional marker yet not pin
point bright to glare other road users.  I've been quite surprised at
how well it has done.  I think that my desire not to outshine the
brighter streetlights works in my favour because of the resulting
colour balance seems normal.
 
 
 

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

Post by Michael Pres » Mon, 07 Dec 2009 13:26:31

In article

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.

The human eye is not more sensitive to red.
It's peak sensitivity is ~560 nm---between yellow and green.

--
Michael Press

 
 
 

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

Post by n.. » Mon, 07 Dec 2009 16:08:53


Quote:
> In article



> > > 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.

> The human eye is not more sensitive to red.
> It's peak sensitivity is ~560 nm---between yellow and green.

(sigh)

  Read the whole thread.

  Mark L. Fergerson

 
 
 

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

Post by Doug » Mon, 07 Dec 2009 22:37:07

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?

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

I'm not certain what's out there now--but as of ~3 years ago, the way to
make a "white" LED was to place a yellow-emitting crystal over a blue
LED. If you studied the spectra emitted, you saw lots of blue, much less
yellow, and nearly none of any other wavelengths. Because of the way
that the blue light is perceived, your mind confuses this as /mostly/
"white".

If you tried to use these white LEDs for high-quality lighting (such as
photography) you would frequently find that they had various ring-shaped
artifacts in the beam, colored either yellow or blue. I've got a cheapie
$12 Cateye 3-AA headlight around somewhere I carry as a backup, that has
a very proiminent center blue spot and yellow edge on the beam.

There may be higher-priced "single" LED setups for cameras now that are
a better balance of white, but for pretty much any flashlights, you
still just get the old blue/yellow.

It is easy to forget--but if you compare a LED flashlight to an
"old-fashioned" incan flashlight, you can see how far off the color
balance of the LED is (in spite of the LED appearing to be much
brighter). The total lack of red wavelengths in the LED is plainly
apparent in a comparison.
~

 
 
 

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

Post by Peter Col » Mon, 07 Dec 2009 23:42:22

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.

That's not at all obvious to me.
 
 
 

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

Post by _ » Tue, 08 Dec 2009 00:07:51

Quote:

> In article



>>> 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.

> The human eye is not more sensitive to red.
> It's peak sensitivity is ~560 nm---between yellow and green.

At low levels yes; at higher levels the blue response is a bit higher (it's
possible that anomalous trichromats have different sensitivities as well as
different peaks, but a) they are rare, and b) I doubt the differences are
great).

True night vision is colourless - matching the emitted colour to the most
sensitive portion of the eye can be a factor in that case - but of course
it is a multi-variate problem with competing factors such as luminous
efficiency, battery weight, cost, percentage of
dim-but-not-true-night-vision cycling, see versus be seen, general
construction and reliability, etctera.

 
 
 

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

Post by Androcle » Tue, 08 Dec 2009 00:38:24


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.

> That's not at all obvious to me.

Then try it and it will be (unless you happen to be blind).
Not that LED bicycle lights were ever intended to illuminate asphalt,
they merely provide a legally required source of light for oncoming
vehicle drivers to observe. If you want to illuminate asphalt, use more
candlepower.

It's obvious (to anyone with eyes and half a brain) that the "white" LED
bicycle lights do not illuminate asphalt roads very well.  Incandescents,
halogens, and sodium lights do better.

 
 
 

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

Post by thirty-si » Tue, 08 Dec 2009 00:44:51


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.

> > That's not at all obvious to me.

> Then try it and it will be (unless you happen to be blind).
> Not that LED bicycle lights were ever intended to illuminate asphalt,
> they merely provide a legally required source of light for oncoming
> vehicle drivers to observe. If you want to illuminate asphalt, use more
> candlepower.

> It's obvious (to anyone with eyes and half a brain) that the "white" LED
> bicycle lights do not illuminate asphalt roads very well. ?Incandescents,
> halogens, and sodium lights do better.

Are "white" LEDs legally white.  As in, a white lamp must be fitted to
the front of the vehicle and a red lamp must (usually) be fitted to
the rear and operational during times of darkness.
 
 
 

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

Post by Frank Krygowsk » Tue, 08 Dec 2009 01:07:30


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.

> > That's not at all obvious to me.

> Then try it and it will be (unless you happen to be blind).
> LED bicycle lights were ever intended to illuminate asphalt,
> they merely provide a legally required source of light for oncoming
> vehicle drivers to observe. If you want to illuminate asphalt, use more
> candlepower.

"Not that LED bicycle lights were ever intended to illuminate
asphalt"?  That's thoroughly wrong.  For just one example, the LED
headlight at http://www.nabendynamo.de/english/index.html is used by
people riding in all-night competitions on the road.

Read some discussion on LED headlights at http://www.peterwhitecycles.com/schmidt-headlights.asp
or at http://www.blayleys.com/articles/lights/page3.htm

It seems you're about a decade behind times ...

Quote:

> It's obvious (to anyone with eyes and half a brain) that the "white" LED
> bicycle lights do not illuminate asphalt roads very well.

... and more than a little rude, as well.

- Frank Krygowski

 
 
 

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

Post by Androcle » Tue, 08 Dec 2009 01:19:22



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.

> > That's not at all obvious to me.

> Then try it and it will be (unless you happen to be blind).
> Not that LED bicycle lights were ever intended to illuminate asphalt,
> they merely provide a legally required source of light for oncoming
> vehicle drivers to observe. If you want to illuminate asphalt, use more
> candlepower.

> It's obvious (to anyone with eyes and half a brain) that the "white" LED
> bicycle lights do not illuminate asphalt roads very well. Incandescents,
> halogens, and sodium lights do better.

Are "white" LEDs legally white.  As in, a white lamp must be fitted to
the front of the vehicle and a red lamp must (usually) be fitted to
the rear and operational during times of darkness.
==========================================
Yes, they are. If you compare older incandescent car headlights
with later halogen lights one will appear to have a yellow tinge
whilst the other appears bluish. Both are legally white.
  http://www.catdiaries.co.uk/images/photography_personal/img_1.jpg
From a legal standpoint you can use a hurricane lamp if you wish,
or even a candle with a glass wind shield. There is no legal requirement
to use an electric light, the law was made before electric lighting
became commonly available.
  http://img1.photographersdirect.com/img/15262/wm/pd1068794.jpg
Legally the lights are required so that you can be seen, not for you to
see by; in Britain a high brightness red rear fog lamp is now a legal
requirement.
 
 
 

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

Post by Androcle » Tue, 08 Dec 2009 01:24:33



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.

> > That's not at all obvious to me.

> Then try it and it will be (unless you happen to be blind).
> LED bicycle lights were ever intended to illuminate asphalt,
> they merely provide a legally required source of light for oncoming
> vehicle drivers to observe. If you want to illuminate asphalt, use more
> candlepower.

"Not that LED bicycle lights were ever intended to illuminate
asphalt"?  That's thoroughly wrong.  For just one example, the LED
headlight at http://SportToday.org/
people riding in all-night competitions on the road.

================================================
Listen up, dim bulb, if you want to illuminate asphalt then use more
candlepower, it's that ***in' simple.

Read some discussion on LED headlights at
http://SportToday.org/
or at http://SportToday.org/

It seems you're about a decade behind times ...

Quote:

> It's obvious (to anyone with eyes and half a brain) that the "white" LED
> bicycle lights do not illuminate asphalt roads very well.

... and more than a little rude, as well.

=============================================
As are you.

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

Post by Just zis Guy, you know » Tue, 08 Dec 2009 02:07:58

On Sun, 6 Dec 2009 15:38:24 -0000, "Androcles"

Quote:

>It's obvious (to anyone with eyes and half a brain) that the "white" LED
>bicycle lights do not illuminate asphalt roads very well.  Incandescents,
>halogens, and sodium lights do better.

Ah, a citation to the International Journal of Because I Said So.
Always the most compelling of arguments, so much better than Andreas
Oehler's much more time-consuming approach of actually testing them
and posting the results.

Guy
--
http://www.chapmancentral.co.uk/urc
GPG public key at http://www.chapmancentral.co.uk/pgp-public-key.txt