The Definition of "Bokeh"
Photo credit: René Coburger / Meyer-Optik-Görlitz
This month Merriam-Webster added “bokeh” to the dictionary. While those of us in the photography world have been using it for years, it’s nice to see official recognition. They define it as “the blurred quality or effect seen in the out-of-focus portion of a photograph taken with a narrow depth of field.” We’d like to expand on that some.
To begin with, bokeh is not confined to images taken at wide apertures and with limited depth of field; although, comments on bokeh are most often made in reference to such images. Bokeh is a term of Japanese origin that refers to the perceived quality of the out-of-focus areas of a photographic image.
An image with good or pleasing bokeh has 3 characteristics:
Out-of-focus image areas are smooth with no harsh linear patterns or other visible artifacts.
The transitions between in-focus areas of the image to out-or focus areas are smooth and gradual rather than abrupt.
The out-of-focus image areas retain the shape of the original object with minimal or no distortion.
Factors influencing bokeh are the optical design of the lens and the physical construction of the lens. Finally, it's worth noting that at this point, statements made about bokeh are inherently subjective, even in cases where there is widespread agreement. Attempts have been made and will continue to be made to quantify the concept of bokeh, but there are presently no universally accepted criteria.