5. Blade count and bokeh

 

The way that out of focus areas, particularly highlights are rendered is referred to as the lens’s bokeh, a Japanese word that is pronounced in a number of ways including boke and bouquet.
Good bokeh is generally considered to have highlights that are rounded rather than having straight sides, for example, forming a hexagon.
The edges of these highlights should also be soft and not haloed or hard-edged. Photographers often describe an out of focus background with good bokeh as being ‘creamy’.
Bokeh is a property of a lens rather than a camera with the optical elements and aperture come into play.
The best results are usually seen when the iris or diaphragm that opens to create the aperture has many blades (9 being typical) that have a rounded edge to create a near spherical opening.
                                       
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