Bokeh
The aesthetic quality of out-of-focus blur in an image. Derived from the Japanese word for blur, it evaluates how pleasing defocused areas appear rather than simply measuring blur amount.
Bokeh refers to the aesthetic quality of out-of-focus areas in a photograph. From the Japanese "暈け" (boke, meaning blur), the term was adopted internationally in the 1990s. Unlike defocus measurement, bokeh evaluates how pleasing the blur appears - a subjective quality assessment of lens rendering.
Bokeh shape and character depend on lens optical design. Point-light bokeh discs directly indicate a lens's bokeh characteristics.
- Aperture blade influence: More blades (9+) produce rounder discs. Fewer blades (5-6) create polygonal shapes. Rounded blade designs help at wider apertures
- Spherical aberration: Under-corrected spherical aberration affects luminance distribution within bokeh discs. Soft, even background bokeh is generally preferred
- Mechanical vignetting: At frame edges, barrel obstruction deforms discs into lemon (
cat's eye) shapes. Stopping down 1-2 stops eliminates this - Onion ring bokeh: Concentric ring patterns caused by aspherical element manufacturing marks in some modern lenses
Computational photography synthesizes bokeh through depth maps and kernel simulation. Smartphone portrait modes apply physically-modeled bokeh in post-processing. CG rendering allows custom aperture shapes for anamorphic or vintage lens effects.