Inspired by this 'bokeh' idea I looked around to see what lenses I had about the house. The most obvious candidates were a couple of Industar 61s on some old FEDs. Lots of people have posted good things about the bokeh from these. They are 39mm Leica screw mount. An adapter for my Sony NEX 5 cost £17.99. The NEX can be set to give a magnification of 7x and 14x for focus assist via a manual button, the camera is set to fire without a lens on aperture priority. You can vary the exposure + or- or set to full manual. So you have a digital camera with manual focus and exposure control and a lens of 80mm equivalent and f2.8.
I took a picture of a garden trolley with the Sony kit zoom at 55mm, the widest it will go at that focal length is f5.6
I then took a similar shot with the Industar, it's 53mm at f2.8.
I'll experiment with it as a portrait lens, and of course I can take full HD video, although I'll need a tripod because it's unstabilised.
I got an M42 adapter for the same price, as I've got a Carl Zeiss Jena off a Practika and some macro tubes to play with.