With the 300mm length I have owned both the standard 300 4.5 and the Nikkor ED 300 4.5. The standard one isnt that flash, not bad, but I wouldnt go berserk about it. The ED 300, which is the first 300 with ED glass and not to be confused with the IF version that most people know, is quite good, but you cannot hand hold easily unless you are using quite fast shutter speed. 72mm filter ring, built in lens hood and rotating tripod collar.
The closest focusing distance is around 4 metres and workable headshots are around the 6 metre mark, once you wish to go for a bust shot then you will be around 7-8 metres away. I did some interesting full-length figure work with the 300 and I used a non-amplified dustbin type megaphone to give instructions, the model was that far away.
The Nikkor ED 180 2.8 is a very nice lens, you will be working around 3-4 metres away for a bust shot, tripod is handy as its a heavy lens if its a long session, but that is your call. This is about the longest lens that seems to work reasonably well for me with portraiture. 72mm filter ring, built in lens hood.
The Nikkor 105 2.5 is nothing short of brilliant; I have taken so many different portraits with this lens that are so good, that even if I never used it for anything else, it would be my best Nikkor lens. However it is brilliant at virtually anything I point it at if this focal length is anywhere near the correct length for what Im shooting. Tight head shots in the vertical format are very nice around the 1.5 2 metre distance and as you pull back to get more of the subject in, it stays the same, brilliant. The best Nikkor lens I have ever used and the best one I own. 52mm filter ring, it has a built in lens hood.
The Nikkor 85 1.4 is not as good at portraiture as the 105, but it is better that the slower 85 f/2, which I have used and find soft. This softness is apparently intended by having lower contrast especially for portraiture. Sort of to reduce wrinkles and blemishes. I wouldnt say it was a bad lens, but its obvious design intentions were apparent whenever I used one, I didnt like it.
Back to the 85 1.4, this lens is really something else, however for portrait work I find that Im getting a bit too close to a model when doing a vertical head shot. It is bitingly sharp, but at a cost of nice out of focus backgrounds that only the 105 and to a lesser extent, the 180 have. 72mm filter ring, no built in lens hood but the Nikon HN-20 lens hood is designed for it and you need it. This lens has floating elements meaning you can focus quite close and quite far (infinity) with quite good contrast. However when used really tight and running at the minimum focusing distance, there is light falloff in the corners, about ½ a stop. Not a problem in the darkroom, but a bit iffy with slide film.
The 135 mm length in Nikon and Nikkor build isnt too flash. The 135 f/2 is fast, but doesnt seem to work too well wide open at all and you find yourself closing the aperture down a couple of stops, I had one for about 2 years and really tried to like it, but in the end it didnt work for me. 72mm filter ring, built in lens hood.
The 105 2.8 Micro Nikkor has floating elements to allow super close up photography, but I dont think it is terrific as a portrait lens, mind you it is pretty damn good, but compared to its far simpler 105 2.5 cousin it isnt in the same league. 52mm filter ring and requires the lens hood supplied with it to be used. A good friend of mine has one of these and we sometimes swap lenses so Im still aware of how it compares to the standard 105.
If I had to suggest which lens, or lenses to think about for portraiture, I would suggest the 105 2.5 as the best by a long shot, it is just right. Then either the 180 2.8 or 85 1.4 depending upon which style of portraiture you favour, or how much room you have behind you.
Mick.