Originally posted by Apapukas It depends what do you call a portrait lens. For whatever reason a lot of people call a portrait and a headshot the same thing. I believe that headshot is only one way of making a portrait. So, pretty much any focal length can be used to create awesome looking portraits (not headshots!).
portrait |ˈpôrtrət, -ˌtrāt|
noun
1 a painting, drawing, photograph, or engraving of a person,
esp. one depicting only the face or head and shoulders.
The most common meaning of portrait IS a headshot.
This why you may sometimes hear "full body portrait" or "full length portrait"--if the word is used by itself, the general assumption is that we're talking about headshots.
To add something to the discussion itself:
If you're looking at a Nikon 85/1.4, then presumably you can afford whatever you want. You could get a Zeiss 85/1.4, or a Pentax 85/x (they were made in several apertures, especially if you count manual focus).
As others have said, if you were comparing the Nikon 85mm on Full Frame to an APS-C usage, you will want to go with a 50 or 55mm instead.