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Posted by Toby on 07/03/06 09:07
"PTRAVEL" <ptravel88-usenet@yahoo.com> wrote in message
news:4grm5rF1o20foU1@individual.net...
>
> "Bill Farnsworth" <bill.farnsworth@verizon.net> wrote in message
> news:7u0qg.168$0G2.59@trnddc07...
>>
>>> PTravel wrote:
>>>> Sodium vapor lights are the common night time illumination in most
>>>> cities in the world, and put out a distinctive yellow light. Because
>>>> they work by exciting sodium atoms, the light output is a very narrow
>>>> spectrum, i.e. it's not just a question of being warmer or cooler --
>>>> there simply are no other bandwidths present. Naturally this results in
>>>> anything being videotaped as appear, essentially, monochromatic (for an
>>>> example, see here:
>>>> http://www.travelersvideo.com/amsterdam%20at%20night.wmv)
>>>>
>>>> Is there any way around this to get, if not a more accurate color
>>>> rendition, at least a more interesting one? Short of bringing my own
>>>> lights, which is not feasible at all, I can't think of anything that
>>>> will add spectra that simply aren't there.
>>
>> Nice stuff Paul.
>> There really isn't much you can do with limited resources other than some
>> correction in post. (bringing a chip chart and shoot that under the light
>> for reference can help later in post)
>> However............
>> Get yourself a rosco cinegel color correction sample set. (1 1/4" x 3")
>> Then you can experiment with white balance through different correction
>> filters.
>> Or add it as correction filtration
>> I'm thinking that something in the Tough Plusgreen family and Tough WF
>> green either added at the lens or subtracted through white balance might
>> bring you a wee bit closer to what you are looking for.
>>
>>
>> Bill F.
>
> Thanks, Bill!
I've looked at sodium discharge lights through a viewing spectroscope. The
two dominant D-lines around 589 nm constitute well over 95% of the light
emission, and that's being generous. They So you have a two-fold problem.
The first is notch-filtering at 589 nm to get rid of the source that is
going to blow everything else out of the water. Then you have the residual
couple of percent to boost up to some level where it does you some good.
Kind of impossible....
Your best bet is to make sure there are some other sources of full-spectrum
light in your shots.
Toby
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