Bokeh (pronounced (bow-keh)
From The Glossary of Digital Photography
Sometimes spelled as bookeh. Bokeh is the English spelling of a Japanese word that means fuzzy or blurry; in photography, it refers to the out-of-focus area of an image. Specifically, it refers to the beauty and aesthetic quality of this portion of an image. The original Japanese word is boke-aji, which was truncated to boke. In March 1997, Mike Johnson, editor of Photo Techniques magazine, added an h to boke to make bokeh, so that readers would pronounce it correctly, instead of rhyming it with joke. The spelling stuck and has been used by most photographers since then. A photograph is made of what is in focus, usually the subject, and the area that is out-of-focus, usually the background and foreground. When the out-of-focus area is attractive—not what is out of focus, but the way it is out of focus—it is said to have good bokeh. The lens and the style of the photographer determine the actual bokeh. Photographs created with a wide-angle lens, for example, usually have very little out-of-focus areas, and thus little bokeh. Telephoto lenses tend to isolate the subject; the background and foreground are more likely to be out-of-focus. Mirror telephoto lenses are generally thought to have unattractive or bad bokeh because of the shape of their circles of confusion, which look like donuts. These blur circles are the out-of-focus areas in the image created by all lenses. They are usually dark with light edges (bad bokeh) or light circles with dark, diffuse edges (good bokeh). Both the coloring of these circles as well as the sharpness of their edges affect the goodness of bokeh. These circles are different due to the construction of lenses and their spherical aberration. Generally, due to the way that circles of confusion are rendered in the image, a lens will have either good bokeh in the background and bad bokeh in the foreground, or the other way around, but not both. Since most people prefer out-of-focus backgrounds to out-of-focus foregrounds, a lens with good bokeh is one that produces good bokeh in the background. Some photographers are skilled at using good bokeh to enhance their images. See also circle of confusion; spherical aberration
