Lensbaby Burnside 35mm f2.8 is the first lens I have seen with a double aperture giving you control over the image of the lens, either giving it a softer slow look or a sharper harser edge bokeh. Both apertures are move independent from each other and there is a special lever on the side to move the front aperture.
Below are the result of moving the apertures and honestly the effect is only just slightly for object close up or even making a portrait shot of a person and its just slightly visible in the bokeh in the background, with one being softer and other with sharper bokeh edges.
Overal its an manual focus lens which make it difficult to use for any beginners, but its really dependable if you need such a control over a lens and if the subtle change really is special enough to buy such a lens for such an effect. Its a full frame lens, but honestly it being 35mm make its quite a wide lens to be able to get much Bokeh with, honestly difference be better visible with a more tele lens where you can get more larger bokeh in the shots.
