RE: [PSUBS-MAILIST] Under Water Lighting

["roger" <rjune@fuse.net>]

The Blue end of the color spectrum travels further in water and
the red end is filtered out first.  So if you want to see farther
use lights that emit more "blue" light and if you want to see true
colors than use a light that puts out more "red" light to compensate
for the filtering effects of water.

Roger J.

-----Original Message-----
From: owner-personal_submersibles@psubs.org
[mailto:owner-personal_submersibles@psubs.org]On Behalf Of Dan h
Sent: Thursday, May 16, 2002 8:43 PM
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] Under Water Lighting


John,

Thanks,  I knew I read somewhere that one end of the spectrum was better
than the
other for under water lights.  I didn't remember where I read it, but it was
probably in the borrowed copy of Busby I had.  The thallium iodide lights
sound a
bit to exotic for my project but the bluish tint of the newer high intensity
auto
lamps are a possibility.  Andre said they require a transformer.  If they're
high
voltage, that might be a problem, but I'll look in to it.

Most of the murkiness in the lake water around here is from plant life.   In
the
Atlantic, upper east coast, it's just murky too.  I don't think I even want
to know
what that's made up of.   ;-)

What do you think about a high intensity lamp, with a slight blue green
filter?
Would a filter help or be to counter productive to make a difference in the
long
run?

Thanks, Dan H.

John Brownlee wrote:

>         Candle-power (or whatever measure of luminence you prefer) is only
> relevant in that it represents the total amount of light energy being
produced.
> A more interesting question is whether that energy will be absorbed or
scattered
> by water and particles in suspension, both on it's way from the lamp to
the
> object and back to your viewport. Remember, there's two passes through the
> attenuating medium to consider when calculating losses.
>         A blue-green color-temperature is really going to help. As for
> scattering, that depends on a lot of parameters. I know that laser line
scanners
> get people around a lot of the problems with incoherent scattering, but
that's
> beyond the scope of lamps. :-)
>         Busby waxed poetic about lamps, I believe his recommendation was
> thallium iodide lamps because their attenuation was low. If you can get
your
> peak flux around 5000 angstroms you'll get more seeing for your watts of
battery
> power.
>
>                                                 Thanks,
>
> --
>                                                         John
>
> John Brownlee
> Chief Systems Administrator
> Scary Monsters Network
> jonnie at scarymonsters dot net