Instead of using multiple images focused at different points to extend the depth of field, can I also reduce it?

Does a technique exist to achieve a shallow depth of field by stacking multiple images that are exactly the same except for focus? An example of a situation one could think would be mimicking extreme shallow depth of field as in a medium format close portrait capture. Indeed, my intended focus stacking method would also not be simple, but theoretically possible.

[Here](http://i.owst.nl/179fdacdb06f480385597d434f971002/opener/2765824.jpg) is an example image of Katja Schuurman.