I have an upcoming project where I've been asked to film floating blue orbs around the talent a la "Starman".
My initial thought is to shoot anamorphic, float a battery powered small source on some monofillament, and composite/track over the source with a light aura of sorts (retaining the flare).
I think this MIGHT work, but in these examples there are clearly larger sources being used. They also seem to be coming from relatively the same area as the orb itself.
Due to the obvious keying/compositing (you can see the black matte lines when watching the film around the