Bokeh is an attractive visual effect that is very popular in photography. It is derived from the Japanese word 'boke', which translates as 'haze' or 'blur'. Bokeh refers to out of focus areas of a photograph caused by the way a lens renders out of focus points of light. This would occur when there is a shallow depth of field (low f-number aperture) and refer to the background area of the image that is outside the depth of field. It can be an aesthetically pleasing effect when it arises from background highlights from light sources as illustrated in the image above.

It can also be an effective technique in portrait photography to enable the subject to stand out from the background, particularly when the background might be distracting. Take a look at the images below. The image on the left hand side is shot with aperture f/4 and yet the background is still quite visible. The image on the right hand side is shot with aperture f/1.8 and with such a shallow depth of field the background is significantly blurred. (They are also shot with different lenses which may be a factor in the slight difference in hue and saturation).

As ever it is possible to imitate these effects in photoshop, with a little help from the blur gallery: