Presidents and paupers, musicians and moviemakers, actors and athletes, writers and regular Joes: I’ve shot hundreds and hundreds of interviews, perhaps thousands, sometimes 25 or more in a single day. But shooting for “Closer to Truth,” the PBS science series on “Cosmos, Consciousness, and God,” presents a unique challenge.

Start with the quest for a dramatic but natural lighting look, while shooting two people talking, with two cameras. Then add the factor that both cameras are moving constantly. Because the cameras will see more than 180 degrees of background during their slow journeys around the room, there’s nowhere to place stands for backlights. And front light just won’t do: flat and boring, out of the question.