> It would allow using full spectrum lighting, and would be easier to selectively filter.
Making a broad spectrum IR filter is far easier than a notch filter for a single visible wavelength. In general it's harder to make more selective filters and an IR filter can be much less selective because the IR band is so large and far away from any visible light.
Also the infrared version would allow using any color background including black, and the on set lighting would appear to the eye exactly as it does to the camera. With the sodium vapor process the bright yellow background would make everything on set look different in person because the eye wouldn't be able to subtract it the way the camera does.
Yes, you would need a filter on any incandescent light. But this is also true of the sodium vapor process. Actually I'm not sure anyone makes a sodium vapor wavelength notch filter suitable for putting in front of an incandescent light. Consequently, as seen in the video, they restricted themselves to special LED lights that emit essentially only three wavelengths. These are very much not full spectrum and will not produce natural colors for some materials. And they had to completely block all windows, whereas for IR you could just install some IR blocking film on the windows and still use natural sunlight.
The whole point of this technique is that you have that sharp frequency band and a crystal / filter that splits like band out.
You're basically proposing something completely different here.
So... while I agree you could do something as you describe, and I'd be interested to see the results of it, I'm not sure what the results would be like.
> The advantages I stated were
>> It would allow using full spectrum lighting, and would be easier to selectively filter.
All I can say is the CC results in that video were pretty great, despite the obvious caveats, compared to green-screen.
If you (or anyone) can build on it to do better, people will be interested in it; but there's obviously a difference between us idly speculating on how/if it might work, and this, where they've actually done it and shown that it does work.
> "they do, it's just uncommon and you haven't heard about it"
No, the point of the technique is you have a frequency band that you can isolate and use in the background and not in the foreground. Using IR instead of visible as your isolated band makes the isolation easier and cheaper with fewer artifacts and limitations. It's still a very similar process otherwise.
Yes, Corridor's results were great. Fewer limitations would make the process even better!
Near ir LEDs are also cheap and easy to power, with its what's in remote controls. Low pressure sodium lights aren't. I remember using them in postgrad labs and it wasn't fun.
Alternatively you could use a solid state laser or narrow band LEDs if you need the band to isolate to be in the visible spectrum too.
> It would allow using full spectrum lighting, and would be easier to selectively filter.
Making a broad spectrum IR filter is far easier than a notch filter for a single visible wavelength. In general it's harder to make more selective filters and an IR filter can be much less selective because the IR band is so large and far away from any visible light.
Also the infrared version would allow using any color background including black, and the on set lighting would appear to the eye exactly as it does to the camera. With the sodium vapor process the bright yellow background would make everything on set look different in person because the eye wouldn't be able to subtract it the way the camera does.
Yes, you would need a filter on any incandescent light. But this is also true of the sodium vapor process. Actually I'm not sure anyone makes a sodium vapor wavelength notch filter suitable for putting in front of an incandescent light. Consequently, as seen in the video, they restricted themselves to special LED lights that emit essentially only three wavelengths. These are very much not full spectrum and will not produce natural colors for some materials. And they had to completely block all windows, whereas for IR you could just install some IR blocking film on the windows and still use natural sunlight.