Why wouldn't your mind like changing light levels? It changes everything else.
You don't always need to summon people though, just go somewhere, they're usually there, and they're almost always there in non lucid dreams. That and light should be like places in a dream. Wherever you are in a dream, you're somewhere, and it's solid mainly. Lights should be the same way.
Speaking from myself (and others') experiences light levels are a little harder to change than anything else.