The aerodynamicist in me gets a little happy when I see shots that have the visible effects of the flow fields around a plane. Shock waves will be the most obvious example, but a trailing vortex can also cause some interesting refraction. The propeller produces a strong vortex from each blade and every once in a while, you can get a shot where the background provides enough of a pattern to allow the prop vortices to show up. I was reviewing some shots from Boeing Field of a Malibu Mirage with the PropJet turboprop conversion when I saw exactly this. Head on it can show quite well but getting it from more of a side on position was a nice surprise. Thankfully, the hangar doors in the background have vertical corrugations and this allows the flow to be seen in both directions due to the upward and downward moving blades.