Posted by PTravel on 07/03/06 18:11

"Toby" <zdftokyo@gool.com> wrote in message
news:44a8ddcd$0$4873$bb4e3ad8@newscene.com...
>
> "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....

I'm not sure it's impossible. Notching 589 nm is certainly possible -- it's
the remaining 5% that I'm interested in playing with.

>
> Your best bet is to make sure there are some other sources of
> full-spectrum light in your shots.

Not an option, unfortunately.

>
> Toby
>

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