bokeh

Bokeh is the aesthetic quality of the blur in out-of-focus areas of a photographic image, particularly how points of light are rendered when not in focus. It is a subjective attribute of a lens’s rendering and should not be confused with general blur caused by incorrect focus or motion.

The look of bokeh is influenced by lens design and camera settings. The shape of the aperture blades affects the outline of out-of-focus highlights; many lenses render circular highlights when the aperture is nearly round. Wider apertures (smaller f-numbers) produce stronger background blur and more pronounced bokeh. Longer focal lengths, greater distances between subject and background, and closer focusing distances increase apparent blur and can enhance bokeh. Optical characteristics such as spherical aberration, coma, and the arrangement of lens elements shape the smoothness or harshness of bokeh, with some lenses showing patterns like onion rings or polygonal edges near the frame.

Etymology and perception: The term bokeh derives from the Japanese word boke, meaning blur or haze, and was adopted into English photography discourse in the late 20th century. In practice, bokeh quality is judged subjectively; photographers describe bokeh as smooth or harsh, pleasing or distracting. The usefulness of bokeh is usually linked to the photographer’s intent and the scene context.

Related concepts: Bokeh relates to depth of field and focal depth, describing how out-of-focus regions are rendered rather than the overall amount of blur. The circle of confusion concept explains how point light sources map to blurred discs in an image, forming the basis for bokeh.