Joel, these things just have a higher frequency, shorter wavelenth so
they penetrate further through water, as could be expected from any
light at that end of the spectrum.  The result is that you can "see"
further in its beam, and the particulate does not backscatter so badly
as with lower frequencies and longer wavelengths. 

As Dr Rose and the Trout suggest, this is why we use them in Leon Sinks
and Weenikulla.

HID is basicly ultra violet.

John R. Rose wrote:
> 
> Joel,
> 
> You really need to try one of these in crap visibility with tanic stained
> lines. The HID light is incredible. It is as though it slices through
> crap water and locks onto the line without all the backscatter you would
> see with a normal bulb. If you are imagining this as simply a brighter
> then you are mistaken. Extrapolation from what you've experienced with
> standard bulbs doesn't hold.
> 
> BTW, I can't imagine why you would want to close your eyes, particularly
> if you are suffering from vertigo. The way to deal with vertigo is to find
> some visual cue. The movement of silt that you can see half an inch or so
> from your mask with your light on is such a cue. The last thing you want
> to do when suffering vertigo is to close your eyes.
> 
> -John
> 
> On Mon, 8 May 2000, Jess Armantrout wrote:
> 
> > you gotta see these things to believe it.  Light sabre is the best analogy.
> >
> >
> >
> > > -----Original Message-----
> > > From: Joel Markwell [mailto:joeldm@mi*.co*]
> > > Sent: Monday, May 08, 2000 2:38 PM
> > > To: Scott Landon; armantrout@mc*.co*
> > > Cc: cavers@cavers.com
> > > Subject: Re: another stupid question..LOL
> > >
> > >
> > > on 5/8/00 12:38 PM, Scott Landon at js_landon@ho*.co* wrote:
> > >
> > > > finally, the correct answer.  trout gets the prize.
> > >
> > > This is a potentially dangerous suggestion. No bright light is
> > > going to cut
> > > through chocolate soup, which I believe is what the original issue was:
> > > total siltout.
> > >
> > > I don't own an HID, but I've seen them in action and unless it has X-Ray
> > > capabilities I can't see how it would do anything but make things worse in
> > > such conditions.
> > >
> > > In variable conditions or LOW vis, sure I can see that, but not
> > > in siltouts
> > > I've been in as one writer indicated where you're chest is in the mud and
> > > your cylinders are on the ceiling.
> > >
> > > The original advice is still the best, line follow and close your eyes if
> > > you experience vertigo.
> > >
> > > Later,
> > >
> > > JoeL
> > >
> > >
> >
> >

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