Bokeh is the visual quality of the blur in the out-of-focus parts of a photograph. It describes how the blur looks, not how much blur there is. The word comes from the Japanese "boke", which means blur or haze. The spelling "bokeh" became popular in English in 1997 through Photo Techniques magazine.
Good bokeh is usually soft and smooth, without harsh edges. Out-of-focus highlights often look round when the lens has many or curved aperture blades. Bokeh depends on the lens design, the aperture and the distance between subject and background.
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