I never heard of this technique before. Very interesting results!

Thanks! :) More of a lens design feature than a technique, really... :) The lens is a copy of an 1840s lens design; you change the aperture by dropping one of these little plates in a slot on the top of the lens:



The ones on the right are some of the normal apertures (those are f16, f5.6, and f2.2); the ones on the left are from the experimental aperture kit I got the other day (there's also a blank one for cutting your own shapes). As you can see in these test shots, it changes the shape of bright out-of-focus spots; with a regular round aperture, all those stars would just be circles. :)

Here's the lens in action:



You can see the aperture plate sticking up (think that was either the 2.2 or the 2.8?); if you click through and check out the test shots in the comments, you can see the normal "swirly bokeh" effects of the lens. :)