When I'm adjusting lighting, I don't do big renders or high render settings. You can get faster turnaround by doing a half-size render. On the render panel, there is a pulldown that usually says "Full". Change that to half for test renders.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)