While Nature Herself has the privilege of playing with light, painters must, in humility, play with pigment. The transference is tricky and many painters don’t play around enough to get the hang of it. Here again, the relationship between photography and painting is useful.
“Bokeh” is a corruption of the Japanese word Boke, which means “blur.” Backgrounds, particularly, are often rendered out of focus. You may be familiar with what are called “circles of confusion,” those round spots of light that occur in photos. Photographers spend some effort to get “good bokeh” as opposed to “bad bokeh.”