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

On Dec 5, 8:26*pm, Michael Press wrote:
In article
,



" wrote:
On Dec 4, 2:50*pm, me wrote:
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

me wrote:
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.
~

me wrote:
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.

On Sat, 05 Dec 2009 20:26:31 -0800, Michael Press wrote:

In article
,
" wrote:

On Dec 4, 2:50*pm, me wrote:
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.

"Peter Cole" wrote in message
...
me wrote:
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.

On 6 Dec, 15:38, "Androcles" wrote:
"Peter Cole" wrote in message

...

me wrote:
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.

On Dec 6, 10:38*am, "Androcles" wrote:
"Peter Cole" wrote in message

...

me wrote:
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 ...


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

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

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

"Just zis Guy, you know?" wrote in message
...
On Sun, 6 Dec 2009 15:38:24 -0000, "Androcles"
wrote:

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 Snipping Guy
Chapman says so.

You were careful to snip
"Then try it and it will be [obvious] (unless you happen to be blind)" to
show
your bias and prejudice, weren't you, ****head?

*plonk*

Do not reply to this generic message, it was automatically generated;
you have been kill-filed, either for being boringly stupid, repetitive,
unfunny, ineducable, repeatedly posting politics, religion or off-topic
subjects to a sci. newsgroup, attempting cheapskate free advertising
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Boringly stupid is the most common cause of kill-filing, but because
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dumb bird to scratch dirt, step back, look down, step forward to the
same spot and repeat the process eternally.

This should not trouble you, many of those plonked find it a blessing
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I hope you find this explanation is satisfactory but even if you don't,
damnly my frank, I don't give a dear. Have a nice day and **** off.

On Sun, 6 Dec 2009 17:13:10 -0000, "Androcles"
wrote:

You were careful to snip
"Then try it and it will be [obvious] (unless you happen to be blind)" to
show
your bias and prejudice, weren't you, ****head?

You set followups to your home group, alt.morons. I guess that your
fellow morons must find this intrusive so I set the groups back to the
right place. No, I didn't snip anything meaningful, the appeal to
what is "obvious" seems to me to be highly questionable with the
current generation of LED headlights, which produce a bright
blue-white light which seems to light up blacktop just fine. The
yellow of sodium vapour lamps is, I believe, more about cutting
through fog and mist than about illuminating blacktop.

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