Obviously, “light” always has an “effect” on TTG photographs.

TTG-qualified photos are entirely created by the recording of visible light; see for example P1, or this FAQ, or this viewpoint page.

But on this website, the term “lighting effects” refers to any light-related visual effect that is different from what the camera lens saw during the exposure(s).

Making the lighting effects in a photograph different from “what the camera saw” is very popular — especially among smartphone photographers, whose devices make it easy and tempting to do—

— but the result is always disqualified by both P2 and P7.