Nikkor 200 mm f/4 AI is a great lens in a small form factor. It is sharp and very well built lens that was introduced in 1977 when Nikon came up with the concept of AI. 200mm occupies is a sweet spot in the variety of focal lengths available. It is not too short as 105 or 135mm lenses. The close-ups of faces look more pleasing due to the change in perspective by using a 200mm lens. The lens is also not as long and heavy as 300mm Nikkors which can be quite uncomfortable for hand-held use.
(Nikon Df with Nikkor 200mm f/4 AI at f/11, 1/100 sec)