Bokeh is a term came from a Japanese word and used in photography to describe spots of blurred areas added with voluntary effort for artistic effect in image. We have published many fine quality photographs as wallpapers those has fine Bokeh. In this article we will go through the optical and artistic sides of Bokeh in Photography.
Bokeh in Digital Photography
As basically it is the quality of optics and other elements that dictates the quality of Bokeh in Photography, there is not much difference in digital photography and Film photography. But, today in digital photography, Bokeh has taken much better turn as we can actually take as many shots we need, unlike Film photography, where one shot rolled a film in not so cost effective way.
Second point is that, We now can see the Bokeh in the preview screen, which is larger than viewfinder to judge the quality.
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What is this Bokeh in Photography
In photography certain subjects like the background is intentionally blurred to minimize the distraction from the main subject. For example, some will appear in the blurred areas (outside the depth of field ) as bright circles, while in others these circles can show a different shape, color or contrast. These different manifestations of the focus and the quality of the transition is called the bokeh.
The bokeh is the blurred area between foreground and background which is out of focus. Bokeh is a very subjective quality and is difficult to measure and is discussed controversially. Many photographers use lenses which can produce good bokeh. Here is an example from our Bokeh and Dew Drop Wallpaper post :

Factors influencing on the construction of the bokeh in photography
Bokeh is influenced by each point of light entering through the disc-shaped aperture of the lens. The properties that cause a lens to produce a nice bokeh, could not yet be clearly defined.
The number and shape of the aperture blades, for example, itself a very uncertain indication of bokeh, although a circular aperture blades are usually considered to create softer bokeh. More the number of blades more circular form is the aperture. Generally tend zoom lenses tend to produce a bad bokeh. Certain basic structures in optical lens design appear more likely than others to be good or bad for bokeh.

Photograph by BenoitPaille. Camera used Canon EOS 5D, with shutter speed of 1/50 second, ISO Speed 800, 50mm
F/1.4 Lens.
A pleasant bokeh is particularly important for fast lenses, as they have the largest aperture and a very shallow depth of field. Bokeh is also important for portrait lenses, because the photographer is often deliberately need shallow depth to the image and make the background blur for artistic effect.
