Have you ever just sat and watched your kids play? 
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Joe and I built a little car this afternoon. It turns on and blasts across the house, but he really prefers to push it. That's straight from the horses mouth. He was pushing it along while watching Octonauts on TV. The light pouring in from the window behind him was so pretty and he got a nice natural reflector on his face from the white sofa he was leaning on.
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I used BBF while observing and photographing. It worked nicely, since he was moving along about the same distance from my camera. I processed using a black and white action from Paint the Moon's Luminosity the Essence set.