It Took Me 30 Years to Solve This VFX Problem – Green Screen Problem [video]

Incandescent lights flicker at twice your AC power frequency -- to a decent approximation, their power is proportional to V^2. But this is input power -- the cooling of the filament is slowish and the modulation depth is low. Most people aren't bothered by this.

Fluorescent lights with old or very crappy "magnetic" ballasts flicker at twice the mains frequency, with deep modulation. The effect on people varies from moderate to extremely unpleasant, and it's extra bad if anything is moving quickly (gyms, etc). There are even studies showing that office workers perform worse under such lighting even if they don't experience personally perceptible symptoms. The effect is so severe that people invented the "electronic ballast", which flickers at much, much higher frequency and avoids low-frequency components. Phew. (The light might still be a nasty color, but the temporal output is okay.)

"Driverless LEDs" are deeply modulated at twice the mains frequency. These are very nasty.

If you actually have a light that flickers at the AC power frequency (certain LED sources in a two-brightness diode-dimmed kitchen appliance fixture will do this, as will driverless LEDs with certain types of failures), then it's extra nasty.

There are plenty of people around who find (depending on the actual waveform) 60Hz flicker intolerable and 120Hz flicker extremely unpleasant. And there are plenty of people who can often perceive flicker under appropriate circumstances up to at least several hundred Hz and even into the low kHz with certain shapes of light sources. You can read up on IEEE 1789 to find a standard based on actual research on what lighting waveforms should look like.

The effect of 120 Hz flicker is bad enough that energy codes in some places (e.g. California) have started to require that LED sources minimize this flicker, but, sadly, it's poorly enforced.

The Disney process had the filter essentially built into the beam splitter, but afaik, nobody knows how to make that happen again (or nobody who knows how, knows it's a desirable thing). Seems like the optics might be cumbersome, but the results seem wortwhile.

Also, you need still need careful lighting, you don't want your foreground illuminated by sodium vapor, but I wonder if you could light the background screen from behind (like a rear projection setup) to reduce the amount of sodium vapor light that reflects from the foreground to the camera.

[1] https://m.youtube.com/watch?v=UQuIVsNzqDk