[Paddlewise] Night Vision

G'Day,

Chuck thanks for pointing to the article - they seem to be having quite a
debate on the subject. At the end of the article he suggests a simple
exeriment comparing different colored LED's.  But as well as the color of
the light what about the intensity rating of the LED? Is a standard LED
bright enough to read maps by? Is an ultrabright LED too bright? I followed
the LED discussion a while ago with a lot of interest in the context of
night kayaking safety lights. On checking our local "Radiospares" or
"Farnell" catalogs (Do you have these in the US?) found there was a huge
difference in the intensity of LED's available, with not much difference in
power consumption. A standard red or yellow LED had 5mcd intensity with
30degree view angle. I found a range of different colored ultrabrights with
an intensity of 250mcd at 25degrees, an ultrabright red "AlGaAs" with
2000mcd at 20degrees, an ultrabright yellow "AllnGaPhas" with an intensity
of 2500mcd at 10degree and an ultrabright green with 3400mcd and 15degrees
view angle. All of them have power dissipations of about 100 to 150mW. The
low intensity LED's cost a few cents, the high intensity ones cost a couple
of dollars (Australian). Does anyone have experience using such LED's for
night kayaking? Also I don't really know if it would work but has anyone
tried using transparent rods as lenses to form sheets of light rather than
cones - less intensity loss with distance?

PeterO.

On 23 Jun 1999 - Chuck Holst wrote

>The gist of the article, published by the American
>Association of Amateur Astronomers, is that light
>intensity, not color, affects night vision most, and that
>green light is superior to red light because green light
>does not have to be as bright as red to read charts and
>instruments. Green also makes many chart colors easier
>to see.

>I've been trying to figure out how to illuminate our deck
>compasses for night navigation. Looks like green LEDs
>might be the way to go.


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