How often does it happen that you are sitting on a park bench, with an unobstructed view of a duckpond and you see a swan spread its wings and fly across the surface of the pond? Not very often, I would wager.
Supposing that does happen to you, what are the chances that you would have a camera with you, round your neck, switched on and have already being taking photos? Even less often!
That happened to me the other week, and I fowled up big time. What could have been a memorable and excellent photo was, instead this
