Date:         Thu, 30 May 1996 12:33:10 -0700
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         John Wakefield <JWakefield@4dmg.net>
Subject:      Re: LED Flashlight Info

Jeff Carver wrote:

> The FlashLED line of aluminum-bodied, water-resistant flashlights
> uses light-emitting diodes instead of an incandescant bulb.  Options
> include red, yellow, green, blue, and IR LED's of several wavelengths
> each.

  Now for what I expect would be the most common end user preferred 
illumination, a white approximation, It seems that the next step is 
learning some sourcing, prices and part numbers.  Then if we get the 
appropriate drive ratio circuitry worked out, running lots of interior 
lights would become much less draining on batteries.
  I'm a little concerned about the efficiency claims, but I understand 
it's a cloudy issue.  Even if and LEDa converted 100% of their eletrical 
flow to light, which they don't, some of the ratios I've seen don't stand 
up.  That is unless you introduce the cloud factor: Human eye sensitivity 
to different radiant "noise."
  A powerfully persuasive argument for this was demonstrated to me by 
someone recently at night while I was riding in a large motorhome.  They 
produced from their pocket one of those double AAA battery powered red 
laser pencil lights.  They're common for around $30 or so these days.  He 
started shining it on objects ahead up to what I'd guess was half a mile. 
If he hit a safety reflector way off in the distance, it appeared as 
brightly illuminated as if it had a large wattage bulb inside it.  This 
goofy light show went on for quite a while until someone finally 
intervened.  At least he kept his beam from other vehicles.
  So the apparent brightness vs. actual meter measured light output is 
what I call the cloud factor preventing straight forward resolution.
  Any thoughts or information on this LED white light approximation 
issue?

  John Wakefield