[LRflex] Re: Was: Concentration; Now: Colour of light. (HELP!)
- From: David Young <dsy@xxxxxxxxxxxxxxx>
- To: leicareflex@xxxxxxxxxxxxx
- Date: Wed, 16 Jul 2008 10:24:10 -0700
At 16/07/2008, you wrote:
Hi David !
The yellow lights you refer to are, in my modest
opinion, low pressure sodium (natrium), discharge lamps.
The light emitted is monochromatic i.e. all the
luminous energy is emitted at a single
wavelength of approx. 5900 Angström (or in a
very, very narrow bandwith centered on that wavelength).
The main advantage of this light source is its
very high efficiency, up to 190 lumens per watt
(to be compared to 20 lumens/watt for quartz halogen filament lamps).
Its main drawback is that its use is limited to
places where colour recognition is not important
(roads, tunnels ...). E.g. a red object will
appear black or very dark brown under this light source.
All the best !
Etienne
Eteinne & Aram:
Thanks for the pointer as to the type of
light. I had assumed that it was LP Sodium, but
was not aware of the severely limited spectrum.
Years ago, Victoria, BC, was one of the first
places to use these lamps for street
lighting. They were encouraged to do so by the
Dominion Astrophysical Observatory, there, which
was suffering tremendous light pollution, as the
city had overgrown the observatory. Since they
do a lot of spectrography, I now see why these
lamps were a huge improvement to the light pollution problem!
Still, it does not help correct the colours in my
photo ... although I am now beginning to think this is not possible.
Thanks, both, for your help.
Cheers!
---
David Young,
Logan Lake, CANADA
Limited Edition Prints at: www.furnfeather.net
Personal Web-site at: www.main.furnfeather.net
Stock Photography at: http://tinyurl.com/2amll4
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