I'm looking to buy a Helios 44 series 58mm f/2 M42 lens for my Nikon D600 and will be mounting it using an M42 to F-mount adapter.
I'm primarily buying this lens for portraits due to the interesting swirly bokeh effect it produces.
There seem to be multiple versions of this lens - 44, 44-2, 44-3, 44-4, 44-5, 44-6 and 44-7 and I'm confused about which one is the sharpest and has the "swirliest" bokeh. I've also searched around on Google, but there seem to be conflicting opinions this regard. In some cases I've read that the newer versions (44-6, 44-7) are sharper but have lesser swirly bokeh effect as it was considered a flaw.
Any opinions will be welcome from individuals knowledgeable in this regard.