Sorry, I'm a newbie and not very eloquent. You're right...for portraits "I" would like a blurred background, which is achieved by close focusing instead of infinity focusing and aperture wide open. You're also right that this lens doesn't seem to fit the bill for portraits (after re-reading this blog a few times). I was not aware that these close-up lenses (without focusing rings) existed and was carried away by the F1.2 of this lens when I first saw it...my mind went immediately to portraits. However, since I got the lens essentially for free, I'll give it a try anyway, and if the portraits don't work I'll play around with close-up shots. I ordered the helicoid and adaptor ring, which will come next week. In the meanwhile, I put a FD-NEX adaptor on my Sony mirrorless, which has a big enough opening to fit the entire M39 end of the lens through. Holding the lens with my hand and moving it back/forth to get focus of my son, I took the attached shot...indoors, at night, F1.2, 1/100 sec, 800 ISO, no flash.
Not really. Almost every camera lens focuses at infinity if it is in the right position with regard to the imaging medium (film, digital sensor ...). Bokeh refers to the out of focus areas. It is qualitative, therefore you don’t really minimize or maximize it. You do get more depth of field the further you are away from an object, however, the object is smaller so you don’t really gain much by doing so. A portrait with the person a half mile away is rather useless.
I’m not sure what you are saying is “ideal for portraits”. Portraits can be wonderful if they are sharp and detailed, or soft and dreamy. There is no “ideal”.
It seems you are thinking that a very small depth of field is a good thing for portraits, therefore this lens shot wide open will be good. I am not expecting that you will be all that satisfied with it. But hope you try and show what you have achieved.