> Bokeh, as I understand it, is controlled mainly > by the aperture blades
No, not really. The aperture blades have an effect on the shape of specular out-of-focus highlights, but the essential characteristics of _bokeh_ have more to do with off-axis aberrations and correction of spherical aberration. So it's essentially part of the lens design itself. The idea that it's all a matter of the aperture blades is a nice simple idea that is gaining some sway on the internet, but it's not really that simple. --Mike
