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Will gelling a sodium vapor light change CRI


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For night exteriors i have usually gelled tungsten lights to get them in the ballpark of sodium or other low CRI city lights.

 

I'm curious if light sources which are inherently give a very low color spectrum will be give a broader spectrum if gelled properly

 

 

for example can I put a little Minus Green and CTB on a sodium light to make the strong color a little more subtle.

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No, a filter by definition only removes wavelengths, it can't add missing ones. So if you put a magenta gel on a partial spectrum source that only has a few color spikes in the green and orange range, mostly what you do is make it dimmer, it doesn't get less green, there aren't opposite wavelengths that become more prominent as a result.

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  • 2 weeks later...

Every cinematographer's kit should include a spectrometer. I used to recommend a Zeiss pocket spectroscope, but hand-held, self-contained spectrometers are now available for just $2000. These instruments show you what's cooking in the suspect "white" light. So you know when two are alike, when filtration might be possible, etc.

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Only $2000? Wow, I had no idea they were so cheap...

 

There's always this sort of solution... One I've been meaning to do when I have some 'spare' time...

 

http://publiclab.org/wiki/desktop-spectrometry-kit-3-0

 

For those who have middle schoolers in the house, this would be a good science fair project.

Edited by John E Clark
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