Choice of portrait lens

Regardless which format I use, zoom or not, whether the lend offer a close focus feature is what I would go for. My own prefernce for portrait, specially the documentary type of portraiture like I did in this series of "Faces of Xinjiang", I want a tighter composition. Although with today high resolution camera like D3X, or for the same matter, Sony Alpha 9 and Canon 1Ds3/5D2, there is a lot of room to crop, refer to my other article on other blog - "Cropping medium format digital portrait". With a normal lens, the picture gives us a very nature perspective image, and this won't change when you crop the image, for example, you don't get the 500mm lens feel if you just crop 10% of the image taken from a 50mm lens, because the 500mm lens gives you an image with the dimension compressed, and 50mm did not. This is similar to the use of a 85mm lens, commonly referred to as a portrait lens - because it gives you a feel similar to natural perspective, more like a normal lens getting closer to the subject, so the picture gives a friendly, more intimat result.
And for the street, market, my pick is 100mm micro.makro lens for 35mm DSLR, as I will do with medium format with 120mm makro or sometimes 100mm lens, particularly the micro/macro lens, because it allows you to get close without the restriction of cloeset focusing of common lens. In this case, the VR capability for the Nikon AF-S 105/2.8 micro, is best for street portrait, at least it is for me, for my way of shoot. The 90mm or 85mm title/shift is also good, but for fast action and VR to give you extra speed in lower light.
And zoom or fixed lens? If I got the choice, certainly fixed lens. Why, because using fixed lens, my concentration can be on the exact comosition I need, so I have to walk/work to get the image I want, with zoom, one tends to stand still, simply zoom and fire off, you can also get picture this way, but to me, I also get lots of waste images from zoom. For zoom lens, I will cover in other article, it has its strength that fixed lens can't match.
Few more pictures taken with Nikon D3X + AF-S Micro VR 105/2.8ED.