[ this is an update of an article which has previously appeared on this website ]

Bokeh is the term used to describe the quality of background blur in a photo,
i.e. how pleasing the blur looks of the background areas. Since the softness of the background blur is usually more important than how the foreground items are blurred, bokeh usually relates to the background blur.

The bokeh of a lens is influenced by numerous factors, including
- the lens design,
- specifically, how spherical abberations are corrected,
- the number of blades in the aperture mechanism,
- focusing distance,
- the actual aperture used will also affect bokeh to some extent,
- the distance of the out-of-focus objects,
- and in the case of the Nikon DC lenses, by how certain aberrations are selectively introduced.

Bokeh is usually described as being subjective, and it largely is.  However, when you’re able to recognize the difference between good bokeh and poor / harsh bokeh, then it becomes less subjective I believe. When you see good bokeh, you’ll recognize it. Same with bad bokeh.

To illustrate how good bokeh appears, and what poor bokeh looks like, I had set up this simple shot.

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