Bokeh is the aesthetic quality of blur produced in unfocused areas of a photograph, and is most visible in the most unfocused areas of highlight. The shape of bokeh is caused by the shape of the aperture in the lens. Through most lenses, bokeh appears as hazy circles. Bokeh can be intentionally used for composition purposes, often to create highlights or to make backgrounds or foregrounds intentionally hazy in order to draw focus to the subject. Some lenses are built specifically to alter the shape and quality of bokeh produced.