I was looking at the shadows as I walked back from getting lunch today. I noticed the difference in shadows between the tree leaves verses unnatural structures, like signs and buildings and stuff. It eventually occurred to me, the shapes of the light through the tree leaves amounted to a natural occurring bokeh effect. It wasn’t something I had heard of before. And google searches don’t turn up much.
But if you look up pinhole cameras on wikipedia, you find out that Aristotle and Euclid both wrote about tree-filtered light being essentially pin-hole camera technology.
So I’m only a few millennia behind the curve.