bokeh

The visual quality of the out-of-focus parts of an image, as distinct from how much of it is out of focus.

Bokeh describes character, not quantity: whether background highlights render as smooth discs or as hard-edged rings, and whether transitions are gentle or nervous. It comes from the Japanese for blur. It matters less in most aviation work, where the subject is distant and the background is sky, and a great deal in ramp and detail shots.

Nearby in Photography

back-lit — Lit from behind, with the light source on the far side of the subject from the camera.
blue hour — The twilight period before sunrise and after sunset when the sky is deeply and evenly blue.
bracketing — Shooting the same frame at several exposures so at least one is right, or so they can be combined.
burst mode — Shooting a rapid sequence of frames while the shutter button is held.