Hi there, I am a D5300 NIKON user and looking for a lens that can render this effect (swirly bokeh). I understand how bokeh is created in general, but would like recommendations as to what lens can render this feature most. I would like the subject to be clear, sharp and crisp. If a few lenses in a price range (low to high) could be recommended that would be great thank you. I love the surreal look of it.
I have and use the Lomography 2.2/85mm Petzval lens for a couple of months now
Despite the furious claims of the 'experts' about inferior IQ, exorbitant price, outdated design etc, I love it, even if it's an aquired taste and needs getting used to.
It can be used to get the swirly background you refer to

Nikon DF Lomography Petzval 2.2/85mm at 2.8
Original at
http://www.pbase.com/paul_k/image/156848401

Nikon DF Lomography Petzval 2.2/85mm at 2.8
Original at
http://www.pbase.com/paul_k/image/156848891
although IMO the more interesting characteristic of the Petzvall lens is the (if focussed properly) contrast between the incredible limited to a pretty small circle, sharpness in the center with the sharp decline outside it.
For portraiture it can give a ultra thin DoF combine with unique boked which is hard to achieve even with lenses as the 1.4/85mm, 2.8/85mm PC or Lensbaby Composer/Edge (Had all of those lenses for that specific aim, and never could get quite the same effect)

Nikon DF Lomography Petzval 2.2/85mm at 2.8
Original at
http://www.pbase.com/paul_k/image/156109862/large

Nikon DF Lomography Petzval 2.2/85mm at 2.8
Original at
http://www.pbase.com/paul_k/image/156857553/large
Note that other lenses fit for use on a (D)SLR offer the same swirlie background feature as well, like the aforementioned nore modern design Helios lens
http://www.nikoncafe.com/xenf/index.php?threads/mc-helios-40-2-85mm-f1-5.281360/#post-3626123
and other Russian made lenses, and at sometimes more moderate prices (although where I live due to VAT, import taxes and transport costs that in the end unfortunately is not the case)
HTH
--
all in a day's work
http://www.pbase.com/paul_k/