Re: [Paddlewise] Night Vision

----Original Message-----
From: Peter Osman

>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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