By that definition the sodium wavelength is naturally emitted too. The sodium vapor process as implemented in the video requires special lights that don't emit

By that definition the sodium wavelength is naturally emitted too. The sodium vapor process as implemented in the video requires special lights that don't emit the sodium wavelength. It's actually much harder to do that (and it affects color reproduction too) than to block some infrared from existing lights. Infrared blocking film and filters are readily available and cheap. They don't need to be fancy narrowband notch filters like a sodium wavelength filter would have to be. Now that I think about it, Disney must have done something pretty special for the lighting in the foreground in their version of the process. They didn't have single wavelength LEDs back then. I wonder how they did it?