I've posted this HDR shot from Edison's Florida lab before, but I just ran across it for the first time in a long time.
When I came into the lab there was no sunshine through the windows, and the only usable light was from incandescent bulbs on the ceiling. But suddenly the sun popped out and shone through the window off to the right of this scene. I raised the camers, propped my elbows against a railing, and shot a HDR burst of ten varied exposures. As soon as the last shot was complete the sun disappeared and never came back the rest of the day.
As Henri Cartier-Bresson said, "It's always luck."
