Bokeh
Videos
In photography, bokeh is the aesthetic quality of the blur produced in out-of-focus parts of an image, whether foreground or background or both. It is created by using a wide aperture lens.
Coarse bokeh on a photo shot with an 85 mm lens and 70 mm entrance pupil diameter, which corresponds to f/1.2
An example of a portrait photo (of Katherine Maher). Note the 'swirly' bokeh.
How the bokeh varies with the aperture.
An extremely shallow depth of field, a common effect in macrophotography, emphasizes bokeh.
Defocus aberration
Videos
In optics, defocus is the aberration in which an image is simply out of focus. This aberration is familiar to anyone who has used a camera, videocamera, microscope, telescope, or binoculars. Optically
A photograph of Christmas lights with significant defocus aberration