Bokeh

Bokeh (derived from Japanese, a noun boke 暈け, meaning “blur” or “haze”) is a photographic term referring to the out-of-focus areas of an image produced by a camera lens using a shallow depth of field. In and of itself, bokeh implies no aesthetic judgment or qualities, either good or bad. Bokeh meaning “blur”, it is only a factual synonym. Which is why, when ones desires to introduce a qualitative judgment on the bokeh seen in a given photograph, one must qualify the concerned bokeh with adjectives such as “smooth”, “silky”, “velvety” or, on the other hand, “coarse”. Likewise, bokeh does not specifically relate to highlight areas ina a photograph : insofar as low light areas can be blurry just as high light ones, such low light areas can exhibit bokeh as well. Bokeh is primarily caused by lens aberrations and aperture shape.