As of yet no physically based renderer that I am aware of can render bokeh how it should actually look. This proposal came about after seeing the anamorphic bokeh recently added. I’m not sure whether or not this is proposal is possible with the current cycles engine, but if so it would hugely improve the results of renders.
The following images (as shown) show when an object is placed on the focal plane, behind the focal plane, and in front of the focal plane.
Correct Focus
Object Too Close
Object Too Far

The first example can be recreated in blender cycles quite well. The other two cannot.
In Focus
Out Of Focus
Out Of Focus With Obstruction

As seen in the diagrams, the obstruction of one object in front of another affects the shape of the bokeh, which is what gives rise to shaped bokeh in a lens; though the object doesn’t have to be within the lens to cause this effect.
If this is not a suitable place to recommend this feature, could someone let me know where a better place to go would be?

Thanks,

Chris Cook.