Photographers have taken a word from Japanese, bokeh (暈け), pronounced “BOW-kah”), to describe the quality of the out-of-focus regions in a photograph. Bokeh is roughly translated as “blur.”
Photographers judge the quality of the bokeh in photographs. Here is a comparison of three different lenses’ bokeh.
Most people consider the left image to have the most pleasing bokeh.
Next: Tertiary effects