Bokeh refers to the aesthetic quality of blur that includes the beauty of the out of focus areas of the image. It highlights the way the lens brings out the magnificence of the out-of-focus points of light.
Bokeh is essentially blurring effect produced by the differences in lens aberrations and aperture shape, which bequeath special effects to the image captured. The effect is generally conferred upon parts outside the depth of field. The photographers use a shallow focus technique to deliberately create bokeh effect on the out-of-focus regions.
Bokeh is a photographic term for blur that comes from the Japanese word boke corresponding to blur quality. The word is used in photography to draw attention to the aesthetics of out-of-focus areas and it is believed that some lenses have the capacity to produce better bokeh effects. The effect can be produced with the macro lenses to obtain pastel colored backgrounds using either 60mm, 105mm or 200mm lens. However, this requires the use of a limited depth of field with an aperture value around f4 or f5.6.
Large aperture lenses like macro and telephoto lenses are used with smaller depth of field and thus bokeh becomes important and easy while using them. The effect finds application in portraiture photography since that requires a stand-out subject against an out-of-focus background. The characteristics of bokeh are generally quantified on the basis of the image’s circle of confusion, and depending upon the lens aberrations, the effect produced varies in quality. The advanced lens manufacturers design lenses with specific controls to manipulate the effect on the out-of-focus areas.
The quality of bokeh greatly depends on the shape of the aperture. Since a limited depth of field is used in the technique, the focus should be on the main part of the subject, generally the eye of the animal. Also, larger apertures require a better flash control for proper illumination and prevention of overexposure. Different lenses work best with different aperture values like f5.6 or f4 for 50mm macro lens, f8 for 105mm macro lens and f11, f8 and f16 for 200mm macro lens while working on bokeh.