In
photography,
bokeh (pronounced
/boʊ'kɛ/) is the blur,
[1][2] or the aesthetic quality of the blur,
[3][4][5] in out-of-focus areas of an image, or "the way the lens renders out-of-focus points of light."
[6] Differences in
lens aberrations and
aperture shape cause some
lens designs to blur the image in a way that is pleasing to the eye, while others produce blurring that is unpleasant or distracting—"good" and "bad" bokeh, respectively.
[1] Bokeh occurs for parts of the scene that lie outside the
depth of field. Photographers sometimes deliberately use a
shallow focus technique to create images with prominent out-of-focus regions. Bokeh is often most visible around small background highlights, such as specular reflections and light sources, which is why it is often associated with such areas.
[1] However, bokeh is not limited to highlights, as blur occurs in all out-of-focus regions of the image.