Rainbows are produced in black studios, we all know about that :)
Here's a quick demo from a recent session with Patricia Hebert. In this one, the cameras are triggered one after the other using a 45ms interval, and this is why you can see the light wrapping up (as opposed to when I trigger all cameras at the same time which is freezing the light). The exposure time is set at 2 seconds and I'm using a pair of Rainbow tubes (https://lightpainting.store)
Light-painting and bullet-time ♡ I have too many cameras. I never have enough cameras.