Re: More on lights.

On Fri, 26 Dec 2008 16:06:52 +0000, Peter Cole wrote:

terryc wrote:
On Fri, 26 Dec 2008 09:01:17 +0000, Keiron wrote:

I read the recent "bright lights" posting which got me in to a bit of
research which in turn revealed that red lights are better for vision
at night as they highlight obstacles with much less depth perception
issues and, whilst highly visible to those around are much less
blinding.

This is one of those areas of research that are interesting, but for
bicycle riders in the realm of sillness.

Think about it?
White light includes red light. Why throw away 7/8ths of the light?

The human eye has rod & cone cells. The rod cells are much more numerous
and 100x more sensitive to light, but they do not distinguish color. The
rod cell response peaks in the blue-green wavelengths, and is virtually
non-existent in reds. Rods give us our night vision, but cone cells give
us color and detail perception.

Some DIY bike light makers have deliberately used blue-green LED's
claiming a many-fold increase in actual perceived brightness. Sounds
good in theory. Red light can be used to preserve night vision because
night vision is insensitive to it.

Ah ok, this is perhaps the point the original source was trying to make
but better expressed here (or better understood I guess).

Red bike lights for illumination of
the road would seem to be a poor idea. Off-road, they'd make foliage
look very dark, another disadvantage.


What do you mean by detail perception in the first paragraph? For example
are there conditions were 3d detail would be increased and 2d decreased
or are such factors linked proportionally? I.e. in context: would red
light at night provide better outline information to the eye i.e. picking
out depth? or are surface and depth details the same?

You don't have to "throw away" light with modern LED lamps. LEDs are
quantum devices which naturally emit at a narrow wavelength. White LEds
are typically made by either blending light from multiple monochrome
LEDs or by exiting a blend of phosphors with a monochrome LED.

What wavelength is this narrow band at or is it atypical?

A monochrome blue-green LED certainly seems more efficient overall when
factoring the spectral sensitivity of the eye.

Fascinating! Thanks Pete, I understand green leds are available
commercially so I'll give them a shot until I have the savvy to build a
set.

Thansk
.

Relevant Pages

  • Re: More on lights.
    ... White light includes red light. ... night vision, but cone cells give us color and detail perception. ... LEds are typically made by either blending light from multiple ... LEDs are available in a variety of wavelengths. ...
    (rec.bicycles.tech)
  • Re: More on lights.
    ... research which in turn revealed that red lights are better for vision at night as they highlight obstacles with much less depth perception issues and, whilst highly visible to those around are much less blinding. ... Rods give us our night vision, but cone cells give us color and detail perception. ... Red light can be used to preserve night vision because night vision is insensitive to it. ... White LEds are typically made by either blending light from multiple monochrome LEDs or by exiting a blend of phosphors with a monochrome LED. ...
    (rec.bicycles.tech)
  • Re: More on lights.
    ... White light includes red light. ... Rods give us our night vision, ... us color and detail perception. ... One practical matter though is that there's a lot more interest in high power white LEDs than blue-green ones, so white LEDs in high wattage have become more available since the time of this article. ...
    (rec.bicycles.tech)
  • Re: night light
    ... Many headlamps etc have extra red LED's for a night vision mode. ... long wavelength red light and it is still used for that purpose. ... BTW peak rod sensitivity is 510nm I misremembered. ... the eye can be a nuisance for fine work or reading. ...
    (sci.electronics.design)
  • Re: Leds colors, just wondering...
    ... > plastic surounding the little diode device? ... Do they put it in a RED medium ... The colored plastic makes it easy to tell what color light the LEDs ... You get red light when it is on, and a but not internally illuminated ...
    (sci.electronics.basics)
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