Originally posted by jfdavis58 This quality depends on several factors: the light, the subject and foreground/background, the lens quality especially the shape and number of blades in the aperture mechanism.
It is effected by the number of aperture blades but not dependent on it, for example you cannot look and go, that lens will produce bad bokeh because it only has 6 aperture blades, and that one will produce great bokeh because it has 9.
It doesn't always work that way, and mainly because when a lens is wide open the aperture blades have no effect, so the bokeh for the two lenses would the be theoretically the same. The way that aperture blades effect bokeh is when stopped down, so a lens with 6 rounded blades would produce a more circular bokeh then a 9 bladed straight aperture. Aperture blades have an effect but it is minimal compared to the overall construction of the lens, the best way to test it is to put it on the camera and take a couple of shots, rather then dismiss the lens based on the quoted aperture blades in the specs.